Visual Basic .NET or Visual Studio software

Launch your Visual Basic .NET or Visual Studio software. When the software first loads, you'll see a screen something like this one: There's a lot happening on the start page. But basically, this is where you can start a new project, or open an existing one. The first Tab, Projects, is selected. At the moment, the area labelled "Open an Existing Project" is blank. This is what you'll see when you run the software for the first time (because you haven't created a project yet). When you create a project, the Name you gave it will be displayed on this page, as a hyperlink. Clicking the link will open the project. At the bottom of the screen, there are two buttons: "New Project" and "Open Project". To get started, click the "New Project" button. When you do, you'll see this dialogue box appear: As a beginner, you'll normally want the option selected: "Windows Application", in the "Visual Basic Projects" folder. This means that you're going to be designing a programme to run on a computer running the Microsoft Windows operating system. If you look in the Name textbox at the bottom, you'll see it says "WindowsApplication1". This is the default name for your projects. It's not a good idea to keep this name. After all, you don't want all of your projects to be called "WindowsApplication1", "WindowsApplication2", etc. So click inside this textbox and change this Name to the following: My First Project Keep the Location the same as the default. This is a folder inside of your "My Documents" folder called "Visual Studio Projects". A new folder will then be created for you, and its name will be the one you typed in the "Name" textbox. All of your files for your first project are then saved in this folder. Click the OK button, and the Visual Basic NET design time environment will open. It will look like the following (the 2008 edition is just the same): That's a very daunting piece of software, hey? Well, don't worry. We'll break it down bit by bit in the next few sections, and pretty soon you'll be zipping your way around it like a pro! In the Visual Basic NET design time environment, the first thing to concentrate on is that strange, big square in the top left. That's called a form. It's actually the pretty bit of your programme, the part that others will see when they launch your masterpiece. Granted, it doesn't look too attractive at the moment, but you'll soon discover ways to lick it into shape. To run the form, try this: • From the menu bar, click Debug • From the drop down menu, click Start • Alternatively, press the F5 key on your keyboard • Your programme is launched Congratulations! You have now created your very first programme. It should look like this: Click the Red X on the form to stop it from running. You will then be returned to the software environment. If you compare the first form with the one above, you'll see that they look very similar. But the one above is actually a real programme, something you could package and sell to unsuspecting village idiots So what's going on? Why the two different views? Well, Visual Basic has two distinct environments, a Design environment and a Debug environment. Design Time is where you get to play about with the form, spruce it up, add textboxes, and buttons, and labels (and code, of course ); Debug is where you can test your programme and see how well it performs. Or doesn't perform, as is usually the case. But don't worry about the terminology, for the time being. Just be aware that there's a two step process to VB programming: designing and debugging. So, let's get on and do some designing! Before we can start designing a form, though, we need some tools. And where are tools kept? In a toolbox! Things like buttons, textboxes, and labels are all things that you can add to your Forms. They are know as Controls, and are kept in the Toolbox for ease of use. The Toolbox can be found on the left of the screen. In the picture below, you can see the toolbox icon next to Form1: To display all the tools, move your mouse over the toolbox icon. You'll see the following automatically appear: There are seven categories of tools available. The toolbox you'll be working with first is the Common Controls toolbox. To see the tools, click on the plus symbol next to Common Controls. You'll see a long list of tools: As you can see, there are an awful lot of tools to choose from! For this first section, we'll only be using the Button, the TextBox and the Label. If you want to keep the toolbox displayed, click the Pin icon next to the X. To close the toolbox, simply move your mouse away. Let's start by adding a textbox to our form. With the tools displayed, do the following: • Locate the TextBox tool • Double click the icon • A textbox is added to your form The textbox gets added to the top left position of your form. To move it down, hold your mouse over the textbox and drag to a new position: Notice the small squares around the textbox. These are sizing handles. Move your mouse over one of them. The mouse pointer turns into an extended line with arrowheads. Hold your left mouse button down and drag outwards. The textbox is resized. Play around with the sizing handles until you're happy with the size of your textbox. One thing you will notice is that you can't make the size any higher, but you can make it wider. The reason why you can't make it any higher is because the default action of a textbox is to have it contain only a single line of text. If it's only going to contain one line of text, Microsoft reasoned, there's no reason why you should be able to change its height. A textbox can only be made higher if it's set to contain multiple lines of text. You'll see how to do this soon. • Create two more textboxes by double clicking on the textbox icon in the toolbar (Or Right-click on the selected textbox and choose Copy. Then Right-click on the Form and choose Paste.) • Resize them to the same size as your first one • Line them up one below the other with space in between • Try to create something that looks like the one below Adding a Label to your Form Let's add some labels near the textboxes so that your users will know what they are for. • Locate the label control in the toolbox • Double click the label icon • A new label is added to your form • It should look like the one below Click on the label to select it. Now hold your left mouse button down on the label. Keep it held down and drag it to the left of the textbox. Create two more labels, and position them to the left of the textboxes. You should now have a form like this one: To see what your Form looks like as a programme, click Debug > Start from the menu bar. Or press F5 on your keyboard: To stop the programme from running, you can do one of the following: 1. Click the Red X at the top right of your Form 2. Click Debug > Stop Debugging from the menu bar 3. Press Shift + F5 on your keyboard You can also click the Stop button on the VB toolbars at the top, as in the image below: All right, we're getting somewhere. We now have a form with textboxes and labels, something that looks like a form people can fill in. But those labels are not exactly descriptive, and our textboxes have the default text in them. So how can we enter our own text for the labels, and get rid of that default text for the textboxes? To do those things, we need to discuss something called a Property. You've probably noticed the area to the right of the design environment, the area with all the textboxes in a grid, the one that has those daunting names like "AccessibleDescription", "AccessibleName", "AccessibleRole". That's the Properties box. Click anywhere on the form that is not a label or a textbox, somewhere on the form's grey areas. The form should have the little sizing handles now, indicating that the form is selected. On the right of the design environment there should be the following Properties box: If your Properties box says "Textbox1 Textbox" or "Label1 Label" then you haven't yet selected the Form. Click away from the textbox or label until the Properties box reads "Form1 Form" What you are looking at is a list of the properties that a form has: Name , BackColor, Font, Image, Text, etc. Just to the right of these properties are the values for them. These values are the default values, and can be changed. We're going to change the value of the Text property. First, you might want to display the list of Properties in a more accessible form. You can display the list properties alphabetically. To do that, click the Alphabetic icon at the top of the Properties box, as in the image below: This will make the properties easier to find. Before we change any in the Properties box, let's clear up what we mean by "Property". What is a Property? Those controls you added to the form (textboxes and labels), and the form itself, are called control objects. You can think of controls as things, something solid that you can pick up and move about. Controls (things) have properties. If your television were a control, it too would have properties: an On/Off button property, a colour property, a volume property, and a ... well, what other properties would your television have? Think about it. The properties of your television will have values. The On/Off button would have just two values - On or Off. The volume property could have a range of values, from zero to ten, for example. If the value of the volume property was set to ten, the loudest value, then you'd probably have some very angry neighbours! In VB.NET, you can change a property of a control from the Properties Box. (You can also change a property using code, which you'll do quite a lot.) If we go back to our Form object, and the properties and values it has, we can see how to change them using the Properties Box. We'll change only one of these values for now - the value of the Text property . So, do this: • Locate the word "Text" in the Property box, as in the image below "Text" is a Property of Form1. Don't be confused by the word "Form1" next to the word "Text". All this means is that the current value of the Text property is set to the word "Form1". This is the default. To change this to something of your own, do this: • Click inside the area next to "Text", and delete the word "Form1" by hitting the backspace key on your keyboard • When "Form1" has been deleted, type the words "My First Form" • Click back on the form itself (the one with the labels and textboxes), or hit the return key on your keyboard • The words "My First Form" will appear as white text on a blue background at the top of the form When you've correctly changed the Text property, your Form will then look like this one: As you can see, your new text has gone at the top of the form, in white on the blue background. So the Text Property of a form is for setting the caption you want to display in the title bar at the top. In the next part, we'll take a look at how to change the text property of labels and textboxes. Changing the values of some properties is fairly easy. We'll now change the Text properties of our labels, and the Text properties of our Textboxes. Click on Label1 so that it has the sizing handles, and is therefore selected. Examine the Property box for the Label: You can see that the Label control has quite a few different properties to the Form control. Think back to your television as an control. It will have different buttons and knobs to your DVD Player control. A label has different "buttons and knobs" to the Form's "buttons and knobs". But the Label has a lot of properties that are the same. The Text property of a Label does what you'd expect it to do: adds text to your label. We'll do that now: • With label1 selected, click inside the area next to "Text", and delete the word "Label1" by hitting the backspace key on your keyboard • Type in the words "First Name" • Click back onto the grey form, or hit the return key on your keyboard • Label1 has now changed its text caption to read "First Name" • If you've made a typing error, go back to the first step above and try again • Your form should now look like this: Now, change the Text property of the other two labels. Change them to these values: Label2: Last Name Label3: Telephone Number What you should notice is that the labels resize themselves, after you press the enter key to commit the changes. You may need to drag your labels to the left a bit. But when you're finished, your form should look like ours below: The form might look a little squashed, though. Is there anything we can do to make it bigger? Well, it just so happens there is. The Form can be resized just like the Label and the textboxes. Click anywhere on the form that is not a textbox or a label. If you look closely around the Form's edges, you'll notice our old friends the sizing handles. To make the form bigger, just stretch them like you did the labels and the textboxes. Play around with the size of the form until you're happy with it. You can now reposition and resize the textboxes and labels so that things don't look too squashed. Your form might look like this one: Click on Debug > Start to have a look at your programme. Or Press F5 on your keyboard. Click Debug > Stop Debugging to get back to the design environment. (Or press Shift + F5, or just click the red X at the top right of the form.) At the moment, our form looks a little bland. Time to liven it up with a splash of colour. Changing the colour of the Form means we have to change one of its properties - the BackColor property. So click anywhere on the form that is not a textbox or a label. If you do it right, you should see the sizing handles around the edges of the grey form. The Property Box on the right will read "Form1", and that indicates that you have indeed selected the form. When the Form is selected you can change its properties. To change the colour of the Form, click the word "BackColor" in the Property Box. Next, click the black down-pointing arrow to the right. A drop-down box will appear. The default colour is the one selected - Control. This is on the System Tab. The System colours are to set whatever colour scheme the user has opted for when setting up their computers. For example, you can use the Display Properties dialogue box in Windows XP to change how things like menus and buttons look. Someone who is colour-blind might have changed his or her settings in order to see things better on the computer screen. If you stick with the System colours then a colour-blind user of your programme would not have any problems seeing your master work. As you can see in the image above, you can choose the colour of the Active Caption. The Active Caption is the one you set earlier when you changed the text to "My First Form". The Active Caption is blue on my computer, and the Active Caption Text is white. It might be different on yours. If you want to choose a colour that is not a System colour, click the Custom Tab. You'll then see this: Click on any of the Colours in the colour palette and the background colour of your form will change. You can also select the Web Tab. When you do, you'll see a list of Web-Safe colours to choose from. A Web-Safe colour is one that displays correctly in a web browser, regardless of which computer being used (that's the theory, anyway). You might want to use a Web-Safe colour if you're designing a project for the internet. But you can choose one even if you're not. To change the colour of the labels, click on a label to select it. Look in the Property box to see if it reads Label. If so, you can now go ahead and change the BackColor property of the Label in exactly the same way that we changed the BackColor property for our Form. Change the colour of the other two labels to anything you like. To change the colour of more than one Label at a time, click on one Label to select it. Now, hold down the "Ctrl" key on your keyboard and click another Label. You'll see that two Labels now have sizing handles around them. Click the third Label with the "Ctrl" key held down, and all three Labels will be selected. You can change the BackColor property of all three at once. If you want to change the Font size of the Labels and Textboxes, select a control. Let's start with Label1. • So click on Label 1 • Scroll down the Property Box until you see Font • Click on the word "Font" to highlight it • MS Sans Serif is the default Font Notice that the Font property has a cross next to it. This indicates that the property is expandable. Click the cross to see the following: Notice that the Font property has a cross next to it. This indicates that the property is expandable. Click the cross to see the following: As you can see, you can change a lot of Font properties from here: the Name of the font, its Size, whether is should be Bold or not, etc. You can also click the square box with the three dots in it. This brings up a dialogue box where you can change the font properties in the same place. Make the following changes to the three labels: Font: Arial Font Style: Bold Font Size: 10 Change the Font of the three Textboxes so that they are the same as the Labels. When you're finished, you should have a form that looks a little more like a real programme. Time now to save your work. Click below to see how to do this in VB .NET. If you have a look in the top right of the Design Environment, you'll see the Solution Explorer. (If you can't see it, click View > Solution Explorer.) The Solution Explorer shows you all the files you have in your project (Notice that the name of your project is at the top of the tree - "My First Project"). At first glance, it looks as though there are not many files in the project. But click the Show All Files icon, circled below: When you click Show All Files, the Solution Explorer will look something like this: When you save your project, you are saving all these files. To save your work, click File > Save All and you'll see the following dialogue box (we've chopped ours down a bit): The files are usually saved in the My Document folder in XP (Document folder in Vista), under Visual Studio. If you want to save your projects elsewhere, click the Browse button. To actually save your work as you go along, just click File > Save All from the menu bar. Or press Ctrl + Shift + S on your keyboard. Or click the icon in the Toolbar (the stack of floppy disks). If you save often then you won't lose any of your work if anything goes wrong with your computer. In the next section, we'll get down and do a bit of actual programming. It's a gentle introduction, so nothing to get too worried about! Time to get our hands dirty with a bit of programming. There's no putting it off any longer, I'm afraid! We'll create a new project for this section. So, if you already have you VB NET software open, you can get rid of the current project by clicking File from the menu bar. From the drop down menu, choose Close Solution. You will be returned to the Start Page. Click the "New Project" button at the bottom. When you get the dialogue box popping up, choose Windows Application at the top. Then change the name from WindowsApplication to Variables. You can keep the location set at the default. When you click the OK button, a new form will appear. If you look at the Solution Explorer at the top, you'll see the name of the project has changed to the Name you gave it. The name of the Project is now Variables - the same name as the folder that is created for you to hold all your project files. Before we get started, it's worth exploring an oddity of the VB Net software. Click on your Form to select it. Then change the Name property to frmVariables. Press the return key on your keyboard to confirm the name change, or just click back on the form: The Name property of your Form has now been changed from Form1 to one of your own choosing (well, ours). Now press F5 to run the project, or click Debug > Start from the menu. Instead of the programme running, you'll probably get this message box: Click the No button to return to the Design Environment. You might now have Task List screen displaying at the bottom of your screen: A rather cryptic message appears: "Sub Main was not found in Variables Form1". You can get rid of the Task List by clicking the X, or the Pin symbol. The reason you got that message is that VB is still trying to run a form called Form1. Even though you changed it's name, it still tries to do something with it. But you no longer have a form called Form1, so VB gives you the error message. Hopefully, Microsoft will correct this in the next version. But here's the solution to the problem. In the Solution Explorer window, right click on the name of your project (Variables). A menu should appear. Click Properties right at the bottom: Notice that we've clicked on "Variables", and not on "Solution Variables". When you click Properties, you get this dialogue box popping up: The Startup Object, as you can see, is still set to Form1. Click the down arrow to reveal the following: The name you gave your form is on the list. Select frmVariables and click the OK button. Now run your programme again. You should get no error messages this time, and the form will load properly. Why are we discussing variables? And what is a variable? With Visual Basic, and most programming languages, what you are doing is storing things in the computer's memory, and manipulating this store. If you want to add two numbers together, you put the numbers into storage areas and "tell" Visual Basic to add them up. But you can't do this without variables. So a variable is a storage area of the computer's memory. Think of it like this: a variable is an empty cardboard box. Now, imagine you have a very large room, and in this room you have a whole lot of empty cardboard boxes. Each empty cardboard box is a single variable. To add two numbers together, write the first number on a piece of paper and put the piece of paper into an empty box. Write the second number on a piece of paper and put this second piece of paper in a different cardboard box. Now, out of all your thousands of empty cardboard boxes two of them contain pieces of paper with numbers on them. To help you remember which of the thousands of boxes hold your numbers, put a sticky label on each of the two boxes. Write "number1" on the first sticky label, and "number2" on the second label. What have we just done? Well, we've created a large memory area (the room and the cardboard boxes), and we've set up two of the boxes to hold our numbers (two variables). We've also given each of these variables a name (the sticky labels) so that we can remember where they are. Now examine this: Dim number1 As Integer Dim number 2 As Integer number1 = 3 number2 = 5 That's code from Visual Basic Net. It's VB's way of setting up (or declaring) variables. Here's a breakdown of the variable Declaration: Dim Short for Dimension. It's a type of variable. You declare (or "tell" Visual Basic) that you are setting up a variable with this word. We'll meet other types of variables later, but for now just remember to start your variable declarations with Dim. number1 This is the cardboard box and the sticky label all in one. This is a variable. In other words, our storage area. After the Dim word, Visual Basic is looking for the name of your variable. You can call your variable almost anything you like, but there are a few reserved words that VB won't allow. It's good practice to give your variables a name appropriate to what is going in the variable. As Integer We're telling Visual Basic that the variable is going to be a number (integer). Well meet alternatives to Integer later. Number1 = 3 The equals sign is not actually an equals sign. The = sign means assign a value of. In other words, here is where you put something in your variable. We're telling Visual Basic to assign a value of 3 to the variable called number1. Think back to the piece of paper going into the cardboard box. Well, this is the programming equivalent of writing a value on a piece of paper Now that you have a basic idea of what variables are, let's write a little piece of code to test them out. First, though, let's have our first look at the coding window. To make life easier, we're going to put a command button on our form. When our command button is clicked, a little message box will pop up. Fortunately, there's no coding to write for a command button, and very little at all for a message box. Instead of double clicking the Button tool in the toolbox to add the control to the form, we'll explore another way to do it. With your Form displayed in the Visual Basic Design environment, do the following: • Click on the Button tool in the toolbox with the left hand mouse button, but click only once • Move your mouse to a blank area of your form - the mouse pointer will turn into a cross • Press and hold down the left mouse button • Drag across the form with the button held down • Let go of the mouse button when you're happy with the size • A Button is drawn You can use the above method to draw most of the controls onto the form - labels, Buttons, textboxes, etc. The Button control, just like all the other controls we've seen so far, has a list of properties. One of these properties is the Text property. At the moment, your button will say "Button 1". You can change that to anything you like. • Click on the Button to highlight it • Click on Text in the Property Box • Click in the box next to the word "Text" • Delete the word "Button 1" • Type "Add two numbers" • Click back on the Form Now add a Textbox to your form using one of the methods outlined (either double-click, or draw). Your Form should now look something like this: The Font property of the Button has also been changed, here, in exactly the same way as we changed the Font property of the Label and Textbox previously. The Text for the Textbox control has had its default Text (Textbox 1) deleted. To get our first look at the code window, double click your Button control. The code window will appear, and will look like this: Notice that we've used the underscore character ( _ ) to spread the code over more than one line. You can do this in your own code, too, if it becomes to long. But you don't have to. The part to concentrate on for the moment is where your cursor is flashing on and off. Because you double-clicked the Button control, the cursor will be flashing between the lines Private Sub … and End Sub. Here's the part we're concentrating on: Private Sub Button1_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles Button1.Click End Sub The part of the code we're interested in is highlighted in red in the code above. Notice, too, that the underscore character ( _ ) has been used to spread the code over more than one line. You can do this in your own code, too, if it becomes to long: Private Private means that no other part of the programme can see this code except for our button Sub Short for Subroutine. The "Sub" word tells VB that some code follows, and that it needs to be executed Button1 This is the name of our button. You might think that we've just erased the word "Button1" when we changed the Text property, so why does VB insist that it's still called Button1? We'll, the Name property of the control is the important one. If you change the Name property, VB will change this button name for you _Click ( ) This is something called an Event. In other words, when the button is clicked, the Click Event will fire, and the code we're going to write will be executed End Sub The subroutine ends right here. This signifies the end of our code Don't worry if you don't understand all of that. It will become clearer later. Let's add our code, which we'll do on the next page. In the previous section, you just designed a form and had your first look at the code window. We'll add some code right now. Click your mouse on the blank line after Private Sub Button1_Click, etc, but before End Sub. Type the following code: Dim number1 As Integer Dim number 2 As Integer Dim answer As Integer number1 = 3 number2 = 5 answer = number1 + number2 MsgBox answer After typing all that, your code window should now look like this: Before we explore what's happening here, save your work and then click Debug > Start from the Visual Basic Menu, or press F5 on your keyboard. This will launch your programme. Click the Button once, and you should get the following: Stop your programming, and return to the Design Environment. If you can't see your code, you can click the Tabs at the top of the Window, as in the image below: Click the "Form1.vb [Design]" tab to see your Form. OK, what happened there? Well, what happened is we've just wrote a programme to add two numbers together, and we displayed the result by using a Message Box - you very first real programme! But let's break that code down a little more. • First, we started with the Dim word, indicating to Visual Basic that we wanted to set up a variable • Then we gave the variable a name (number1) • Next, we "told" VB that what is going inside the variable is a number (As Integer) • Two more variable were set up in the same way, number2 and answer After setting up the three variables, here's what we did: • Told Visual Basic that what is going into the first variable was the number 3, and what is going into the second variable was the number 5. To put something into a variable, you use the equals ( = ) sign. But it's not really an equals sign - it's an assignment operator. You are assigning the value of 3 to the variable called number1 number1 = 3 number2 = 5 The next part is a little bit more complicated, but not too complicated. What we wanted to do was to add two numbers together. So we said number1 + number2 Visual Basic already knows how to add up: all we need to do is "tell" it to add up. We do the "telling" in the traditional, mathematical way - with the plus sign (+). What Visual Basic will do is to look at what we've stored inside number1, and look at what's inside number2. It's sees the 3, sees the five, and also sees the plus sign. Then Visual basic adds them up for you. Except we also did something else. We said to Visual Basic "When you've finished adding up the two variables number1 and number2, store the result in that other variable we set up, which is called answer." So, the whole line answer = number1 + number2 means: "Add the variable called number1 to the variable called number2. Then store the result in the variable called answer." Think of it as working from the right-hand side of the equals sign first. Then when you have the answer, assign it the variable on the left of the equals sign. The final part of the programme used Visual Basic's in-built Message Box. We'll learn a more about the Message Box later. For now, think of it as a handy way to display results. Message boxes are quite handy when you want to display the result of some code. But we have a textbox on the form, and we might as well use that. So delete the line: MsgBox answer. Type the word Textbox1, then type a full stop. You should see a drop-down box appear. This is a list of the Properties and Methods that the Textbox can use. Scroll down until you see the word "Text". Double click the Text property and the drop-down box will disappear. (This drop-down box is known as IntelliSense, and is very handy. It means you can just select a property or method from the list without having to type anything.) The Text property you have chosen is the same Text property that you set from the Properties Window earlier. Here, we're setting the property with our code; before, we set it at design time. But the result is the same - the Text property of the textbox will be set to a value of our choosing. To set a value, type an equals sign, then type a value for the Text property. We want the contents of the variable called answer to appear in the textbox. So the rest of the code is just this: Textbox1.Text = answer Your code window should then look like this: Run your code again, and press the Button on the form. You should see the number 8 appear in the textbox. OK, time for your first exercises. They're not too painful, and hopefully they'll giver you a better idea of what variables are. And besides, programming is about doing, not talking. So off we go! Exercise Delete the values "3" and "5" and replace them with numbers of your own Exercise Delete the plus sign in between number1 and number2, and replace them with each of the following in turn - (the minus sign) * (the multiplication sign in VB is the asterisk sign) / (the divide sign in VB is the forward slash) Exercise Set up another Integer variable. Give it the name number3. Assign a value of 10 to this new variable. Multiply the value of your new variable by the variable called answer. Display the result in your textbox. (Another way to assign values to variables is when you first set them up. You can do this: Dim number3 As Integer = 10 This is exactly the same as saying: Dim number3 As Integer number3 = 10 It's up you which method you use. But the objective is the same - to assign a value to a variable.) In the next part, we'll about a different kind of variable - a string variable. So we've learnt something about variables, what they are and how to set one up. We learnt about the word "integer", and that integer variables held numbers. But what if we don't want numbers? After all, our first Form asked users to type in their First Name and Last Name. Names are not numbers, so what do we do then? Well that's where Strings come in. What is a String? Actually a string is nothing more than text. And if we want Visual Basic to store text we need to use the word "String". To set up a variable to hold text we need to use As String and not As Integer. If the information we want to store in our variables is a First Name and a Last Name, we can set up two variables like this. Dim FirstName As String Dim LastName As String Again we've started with the Dim word. Then we've called the first variable FirstName. Finally, we've ended the line by telling Visual Basic that we want to store text in the variable - As String. So we've set up the variables. But there is nothing stored in them yet. We store something in a variable with the equals sign ( = ). Let's store a first name and a last name in them FirstName = "Bill" LastName = "Gates" Here, we said to Visual Basic "Store the word 'Bill' into the variable FirstName and store the word 'Gates' into the variable called LastName. But pay attention to the quotation marks surrounding the two words. We didn't say Bill, we said "Bill". Visual Basic needs the two double quotation marks before it can identify your text, your String. So remember: if you're storing text in a variable, don't forget the quotation marks! To test all this out, add a new Button to your Form. Set the Text property of the Button to "String Test". Your Form would then look like this: Double click your new button, and add the following code: Dim FirstName As String Dim LastName As String Dim FullName As String FirstName = "Bill" LastName = "Gates" FullName = FirstName & LastName Textbox1.Text = FullName Your code window should now look like this (some of the first line has been cropped in the image below): There's a line there that needs explaining FullName = FirstName & LastName In the two lines of code above that one, we stored the string "Bill" and the string "Gates" into two variables. What we're doing now is joining those two variables together. We do this with the ampersand symbol ( & ). The ampersand is used to join strings together. It's called Concatenation. Once Visual Basic has joined the two strings together (or concatenated them), we're saying "store the result in the variable called FullName". After that, we tell VB to display the result in our Textbox. So, once you've typed the code, start your programme and test it out. Once the programme is running, Click the Button and see what happens. You should have a Form that looks something like this one: The textbox displays the text stored in our variables, "Bill" and "Gates". We joined them together with the ampersand ( & ). But as you can see, the two words are actually joined as one. We can add a bit of space between the two words by using another ampersand. Change this line FullName = FirstName & LastName to this: FullName = FirstName & " " & LastName What we're saying here is join this lot together: the variable called FirstName and a single blank space and the variable called LastName. When you've finished concatenating it all, store the result in the variable FullName. Notice that we don't surround FirstName and LastName with quotation marks. This is because these two are already string variables; we stored "Bill" into FirstName and "Gates" LastName. So VB already knows that they are text. Exercise Remove one of the ampersand symbols (&) from this line in your code: FullName = FirstName & " " & LastName Move your cursor down a line or two. You should see that part of your code has a wiggly blue line under it: VB is telling you that it has problems with this line of code. If you hold your mouse over the wiggly blue line, VB tries to provide an explanation: The explanations VB provides are sometimes enigmatic. But you will know that there is a problem. If you run the code, you'll get this popping up at you: Click the NO button. Put the ampersand back in, and all will be well. Exercise Amend your code so that the textbox reads Gates Bill when the Command button is clicked. Exercise Add another string variable to your code. The variable should hold a middle name. Display the first name, the middle name and the last name in the textbox. Points to remember: • Your variable names cannot include spaces. So the variable MiddleName would be all right, but Middle Name will get you an error message • When you're putting text into your new variable, don't forget the two double quotes • Remember to put in enough ampersands in your FullName = line of code In the next part, we'll take a look at how to asign text from a textbox into our string variables. Instead putting direct text into your variables, such as "Bill" or "Gates", you can get text from a textbox and put that straight into your variables. We'll see how that's done now. First, do this: • Add a new textbox to your form • With the textbox selected, locate the Name property in the Properties area: The current value of the Name property is Textbox2. This is not terribly descriptive. Delete this name and enter txtLastName. Scroll down and locate the Text property. Delete the default text, and just leave it blank. Click on your first textbox to select it. Change the Name property from Textbox1 to txtFirstName. What we've done is to give the two textboxes more descriptive names. This will help us to remember what is meant to go in them. Unfortunately, if you view your code (click the Form1.vb tab at the top, or press F7 on your keyboard), you'll see that the blue wiggly lines have returned: If you hold your cursor of the Textbox1, you'll see this: It's displaying this message because you changed the name of your Textbox1. You now no longer have a textbox with this name. In the code above, change Textbox1 into txtFirstName and the wiggly lines will go away. (Change it in your Button1 code as well.) Your code should now read: txtFirstName.Text = FullName Run your programme again. If you see any error messages, stop the programme and look for the wiggly lines in your code. We'll now change our code slightly, and make use of the second textbox. You'll see how to get at the text that a user enters. Locate these two lines of code FirstName = "Bill" LastName = "Gates" Change them to this FirstName = txtFirstName.Text LastName = txtLastName.Text Remember: the equals ( = ) sign assigns things: Whatever is on the right of the equals sign gets assigned to whatever is on the left. What we're doing now is assigning the text from the textboxes directly into the two variables. Amend your code slightly so that the Whole Name is now displayed in a message box. Your code should now be this: Dim FirstName As String Dim LastName As String Dim WholeName As String FirstName = txtFirstName.Text LastName = txtLastName.Text WholeName = FirstName & " " & LastName MsgBox(WholeName) Run your programme. Enter "Bill" in the first textbox, and "Gates" in the second textbox. Then click your "String Test" button. You should get this: Before we changed the code, we were putting a person's name straight in to the variable FirstName FirstName = "Bill" But what we really want to do is get a person's name directly from the textbox. This will make life a whole lot easier for us. After all, not everybody is called Bill Gates! In the line FirstName = txtFirstName.Text that is what we're doing - getting the name directly from the textbox. What we're saying to Visual Basic is this • Look for a Textbox that has the Name txtFirstName • Locate the Text property of the Textbox that has the Name txtFirstName • Read whatever this Text property is • Put this Text property into the variable FirstName And that's all there is too reading values from a textbox - just access its Text property, and then pop it into a variable. Exercise • Add a third textbox to your form • Change its Name property to txtWholeName • Add labels to your form identifying each textbox (A quick way to add more labels is to use the toolbox to add one label. Then right click on that label. Choose Copy from the menu. Right click on the form, and select Paste.) • Write code so that when the "String Test" button is clicked, the whole of the persons name is displayed in your new textbox When you complete this exercise, your form should look like this one (we've deleted the first button and its code, but you don't have to): In the next part, we'll explore some more variable types you can use. We've met two variable types so far - As String and As Integer. But there are quite a few more you can use. Let's start by examining number variables. Start a new project for this. If you have the old one displayed, you can click File > Close Solution from the menu bar. You will then be returned to the Start Page. Click the New Project button at the bottom. In the dialogue box, give your project a name. Put a textbox and a Button on your new form. Change the Properties of the Textbox to the following Name: txtNumbers Font: MS Sans Serif, Bold, 10 Text: just delete the default Textbox1, and leave the textbox blank Change the Properties of the Button to the following: Text: Answers Font: MS Sans Serif, Bold, 10 Click on the Form itself, and change it's Text property to "Testing Types". Your Form should look something like this: Double click on the Button to bring up the code window. Type the following code for your Button (The Button1_Click part is spread over three lines only for ease-of-reading on this web page. You can keep yours on one line in your code): Private Sub Button1_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles Button1.Click Dim testNumber As Short testNumber = txtNumbers.Text MsgBox testNumber End Sub Notice that there is a new Type of variable declared - As Short. This means "Short Integer". We'll see what it does. Run your programme. While it's running, do the following: • Enter the number 1 into the textbox, and click the Answers button • The number 1 should display in the Message Box • Add the number 2 to the textbox and click the Button • The number 12 should display in the Message Box • Add the number 3 to the textbox and click the Button • The number 123 should display in the Message Box • Keeping adding numbers one at a time, then clicking the button How many numbers did you get in the textbox before the following error message was displayed? (Click Break to get rid of it.) You should have been able to enter 12345 quite safely. When you entered 123456 and clicked the button, that's when the error message displayed. When you click the Break button, you are returned to the coding environment. You'll see the problem line highlighted in yellow: But your programme will still be running. So click Debug > Stop Debugging to return to the normal code window. An Overflow happens when you try to put too much information into a variable that can't handle it. The reason we got an error message after just 6 numbers was because of the variable type. We had this Dim testNumber As Short And it's As Short that is causing us the problems. If you use As Short you're only allowed numbers up to a certain value. The range for a Short variable is -32 768 to 32 767. When we entered 6 numbers, Visual Basic decided it didn't want to know. If you run your programme again, and then enter 32768, you'll get the same Overflow error message. If you change it once more to -32769, you'll get the error message as well. So it's not just 6 numbers a Short Type can't handle - it's 5 numbers above or below the values specified. So what's the solution? Change the variable Type, of course! Change the variable to this Dim testNumber As Integer Now start the programme and try again, adding numbers one at a time to the textbox, and then clicking the Command button. How far did you get this time? If you started at 1 and added the numbers in sequence, you should have been allowed to enter 1234567890. One more number and Visual Basic gave you the Overflow error message, right? That's because variable types with As Integer also have a limitation. The range you can use with the As Integer variable type is -2,147,483,648 to 2,147,483,647. If you want a really, really big number you can use As Long. Dim testNumber As Long But these will get you whole numbers. Leave your number on As Integer. Run your programme again and enter a value of 123.45 into your textbox. Press the button and see what happens. VB will chop off the point 45 bit at the end. If you want to work with floating point numbers (the .45 bit), there are three Types you can use: Dim testNumber As Single Dim testNumber As Double Dim testNumber As Decimal Single and Double mean Single-Precision and Double-Precision numbers. If you want to do scientific calculations, and you need to be really precise, then use Double rather than Single: it's more accurate. The As Decimal Type is useful when you want a precise number of decimal places. It's not as accurate as the Double Type, though. In terms of the space used in the computer's memory, Short Types use 2 Bytes, Integer Types use 4 Bytes, Long Types use 8 Bytes, Single Types use 4 Bytes, Double Types use 8 Bytes, and Decimal Types use 16 Bytes. Exercise Write a programme to calculate the following sum. 0.123345678 * 1234 Use the Single Type first, then change it to As Double. Use a Message box to display the answer. Was the number rounded up or rounded down for the Single Type? In the next part, we'll get some more practise with variables. In this next section, we're going to learn how to transfer the contents of one textbox to another textbox. We'll also learn to transfer the text from a label to a textbox, and whatever was in the textbox we'll transfer it to a label. This will get us a little more practise with variables, and how to use them. Ok, start a new Visual basic project. You should know how to do this by now, and what the design environment looks like. But you should have a plain grey Form on your screen. By default it will be called Form1. Make sure the Form is selected (has it got the white squares around it?), and the click the Name property in the Properties window. Change the Name of the form to frmVariables. Set the Text property of the Form to "Transferring information". You can choose any background colour you like for the form, or leave it on the default. Put the following controls on the Form, and change their properties to the one's specified below (NOTE: lbl is short for label): Textbox Name: txtVariables Font: MS Sans Serif, Bold, 10 Text Delete the default text "Text1" and leave it blank Label Name: lblTransfer BackColor: A colour of your choice Text: Label Caption Font: MS Sans Serif, Bold, 10 Button Name: btnTransfer Text: Transfer The height of your controls is entirely up to you. If you double click your Button to bring up the code window, you will see that the first line of the code no longer says Button1_Click (etc). The first line should say this Private Sub btnTransfer_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles btnTransfer.Click End Sub The reason it has changed is because you changed the Name property of the Button. The button now has the Name btnTransfer. If you wanted to, you could change the Name property back to Button1. Then when you double clicked the button, the code window would pop up and the first line would be Button1_Click(etc ). What we're going to do now is to transfer the Text on the label ("Label Caption") to our empty textbox. And all with the click of a button. As you'll see, there isn't much code. Type the following into your code window: Dim LabelContents As String LabelContents = lblTransfer.Text txtVariables.Text = LabelContents Your code window should now look something like this: Now Run your programme and test it out. When you click on the "Transfer" button, you should see that the contents of the label will be inserted into the textbox: But let's break the code down and see what's going on. Dim LabelContents As String Here is where we set up a variable called LabelContents. Because it will be holding text, we've used the variable type As String. LabelContents = lblTransfer.Text Here is where we put something into our empty variable. We changed the Name property of our Label from the default Label1 to lblTransfer. A Label has lots of properties you can manipulate. One of those properties is the Text property. After you typed the word "lblTransfer" and then typed a full stop, you probably saw a drop down box appear. Inside the box is a list of all the properties and Methods that a Label has. We wanted to manipulate the Text property of our label so we selected the word Text after the full stop. So we were saying "Access the value of the Text property of the label called lblTransfer, and put this value into the variable called LabelContents." Because our Text was ""Label Caption", the variable LabelContents now holds the text "Label Caption." txtVariables.Text = LabelContents Finally, we want to transfer whatever is in the variable LabelContents to the Textbox. Our Textbox is called txtVariables. Again, after typing the full stop the drop down box would appear, showing you a list of all the properties that a Textbox has. The one we're interested in is the Text Property. So we're saying, "Take whatever text is in the variable LabelContents, and transfer it to the Text property of the Textbox called txtVariables. And with three lines of code we can transfer text from a label to a Textbox. But can we do it the other way round? Can we transfer whatever is in a Textbox to a Label? Well, sure we can. Add another button to your form. Change its Name property from Button1 to cmdTransferToLabel, and change the Caption property to "Transfer To Label". Again, there's just three lines of code. So double click your new button to bring up the code window. Then type in the following code: Dim TextBoxContents As String TextBoxContents = txtVariables.Text lblTransfer.Text = TextBoxContents Now, see if you can work out how it works. It's the same thing as the first three lines of code: set up a variable, transfer the Text property of the Textbox to the variable, transfer the variable to the Text property of the Label. Run your programme and test it out. Type something into the Textbox, and then click the "Transfer To Label" button. Exercise A button also has a Text Property. Write code to transfer the Text property of a button to the Textbox. It's probably better for this exercise to create a new Button. Set its Name property to whatever you like. And give its Text Property a new value (The Text property will be Button1 by default) . But the process is exactly the same as the two bits of code above - you should only need 3 lines of code for this exercise. • Set up a Variable • Transfer the Text property of the button to the variable • Transfer the variable to the Textbox In the next part, we'll start a Calculator project. This will get you some more practical experience of working with variables. In the next few pages, you're going to create a Calculator. It won't be a very sophisticated calculator, and the only thing it can do is add up. What the project will give you is more confidence in using variables, and shifting values from one control to another. So create a new project, call it Calculator, and let's get started. Designing the Form Let's design the form first. What does a calculator need? Well numbers, for one. A display area for the result. A plus sign button, an equals sign button, and a clear the display button. Here's how our calculator is going to work. We'll have 10 button for the numbers 0 to 9. When a button is clicked its value will be transferred to a display area, which will be a Textbox. Once a number is transferred to the Textbox we can click on the Plus button. Then we need to click back on another number. To get the answer, we'll click on the equals sign. To clear the display, we'll have a Clear button. If you haven't already, create a new project. Save it as Calculator. To your new form, first add ten Buttons (You can add one, then copy and paste the rest). The Buttons should have the following Properties: Name: btn Plus a Number (btnOne, btnTwo, btnThree, etc) Text: A number from 0 to 9. A different one for each button, obviously Font: MS Sans Serif, Bold, 14 Next, add a Textbox. Set the following properties for the Textbox: Textbox Name: txtDisplay Font: MS Sans Serif, Bold, 14 Text: Erase the default, Textbox1, and leave it blank Three more Command buttons need to be added Plus Button Name cmdPlus Font MS Sans Serif, Bold, 14 Text + Equals Button Name cmdEquals Font MS Sans Serif, Bold, 14 Text = Clear Button Name cmdClear Font MS Sans Serif, Bold, 14 Text Clear When your form design is finished, it might look something like this: So if you wanted to add 5 + 9, you would click first on the 5. A 5 would appear in the textbox. Then you would click the + symbol. The 5 would disappear from the textbox. Next, click on the 9. The number 9 would appear in the textbox. Finally, click on the = symbol. The 9 would disappear from the textbox, and the answer to our sum would replace it. We would then click the Clear button to clear the display. In the next section, we'll make a start on the VB NET code for the all those buttons. In the previous part, you designed the NET form for your calculator. We'll now make a start on the code. You might be thinking that all this is terribly complicated at such an early stage. But it isn't really. All we are doing is transferring the Text Properties from the Buttons to the textbox. And you already know how to do that. The number buttons don't do anything else. All the work is done with the Plus button and the Equals buttons. And there's only two lines of code needed for the Plus button, and three for the Equals button. For this to work, though, a little word about Scope in VB NET. So far, when you've set up a variable, you've set them up behind a Private Subroutine. Like this: Private Sub Button1_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles btnZero.Click Dim MyVariable As String End Sub Suppose you had another button on the form, Button2, and the code was this Private Sub Button2_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles btnZero.Click Dim MyOtherVariable As String End Sub How can you access what's in MyVariable from Button2? The answer is, you can't. It's like two people sitting at desks in cubicles. Each person has written something on a piece of paper. They can't see into the other person's cubicle, only whatever is their own cubicle. So how do they share their information? Well suppose there is a screen in front of them. A big screen. They can both see the screen in front of them; it's each other they can't see. What they could do is project their information onto the screen. Then one person could see what the other has written. Similarly, in VB you can set up your variable declarations outside of the code for a Button. That way, more than one Button can see the code. You can place your variable declarations right at the top of the code window, just beneath the line that begins "Public Class Form1". We'll set up two Integer variables there, total1 and total2: Now all the controls on your form can see these two variables. Those Buttons you set up can put something in them, and every button has the ability to see what's inside them. The 0 to 9 Buttons The Buttons with the Text 0 to 9 only need to do one thing when the button is clicked - have their Text Properties transferred to the Textbox. You've already wrote code to do that. So double click the 0 Button and enter the following code: Private Sub btnZero_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles btnZero.Click txtDisplay.Text = btnZero.Text End Sub This code will transfer the Text Property of a Button called btnZero to the Text Property of a Textbox called txtDisplay. Run your programme and try it out. When the programme is running, click the 0 button to see that it does indeed transfer the Text on the Button to the textbox Except, there's a problem with that code. If you wrote similar code for all ten of your number buttons, the calculator wouldn't be right. Why is that? Have you spotted what's wrong? It's a good idea to set this book aside for a while and think about why this code on it's own wouldn't work. In fact you could write code for a few more of the number buttons and test it out. What happens when you transfer the number 2 to the Textbox, and then click the number 3? The number 2 will disappear, to be replaced by the number 3. Which is all right if all you wanted to do was add up single numbers, but not much good if you actually wanted the number 23 in the Textbox. With this code, you could have either the number 2 in the Textbox or the number 3, but not both! So how do we solve this problem? How do we fix it so that we can have two or more numbers appearing in our Textbox? What we need is a way to get whatever is in the Textbox to stay where it is, and not disappear on us when we click a different number. It's quite easy. It's this: txtDisplay.Text = txtDisplay.Text & btnZero.Text So now we're saying the textbox doesn't just contain the Text on the Button. It must also keep whatever is inside the textbox as well. So what you need to do now is to add that code to all of your ten number Buttons. Obviously it won't be exactly the same. For the button called btnOne the code would be this: txtDisplay.Text = txtDisplay.Text & btnOne.Text When you've finished coding all ten buttons, run the programme and click all ten number button to see if they do indeed transfer the numbers on the caption to the textbox. Not only that, but test to see if you can have more than one number in the textbox. Now that we can get numbers into our Textbox display area, we'll write code to do something with those numbers - add them together, in other words. We'll do that in the next part. Click the link below to move on. he message box function you have used so far is the old message box function. It is the one left over form VB6: MsgBox("Your Message Here") The new VB.NET message box function is very similar, but the way you use it is slightly different. It's this: MessageBox.Show("Your Message Here") So you type the word "MessageBox" then a full stop. Double click the "Show" method on the menu the appears. Then type a round bracket. You should get a rather long and complex tool tip appearing. In fact, it's too long to even fit on this page! What it all means is there are options you can use with your message box. The first one is "text As String". The text in question is the text that will appear for your message - the message itself, in other words. The next one is "caption As String". This sets the white caption at the top of the message box. So if your message box function was this: MessageBox.Show("This menu will Undo an Operation", "Undo") You would get this message box popping up: Each option for your message box is separated by a comma. If you type a comma after the "Undo" in the code above, you'll get another pop-up menu. On this menu, you can specify which buttons you want on your message box: If you only need the OK button on your message boxes, then double click this item, then type a comma. Yet another pop-up menu will appear. On this menu, you can specify the symbol that appear in the message box: It's up to you which symbol you choose. Experiment with all of them and see what they look like. In the image below, we've gone for the Information symbol: Compare the message box above with the one we had earlier: In a real programme, you should use the new MessageBox.Show( ) function, rather than the MsgBox() we used (and will again because it saves on typing and space!) What is conditional logic? Well, it's something you use in your daily life all the time, without realising you're doing it. Suppose that there is a really delicious cream cake in front of you, just begging to be eaten. But you are on a diet. The cake is clearly asking for it. So what do you do, eat the cake and ruin your diet? Or stick to your diet and let somebody else have that delicious treat? You might even be saying this to yourself: If I eat the cake Then my diet will be ruined If I don't eat the cake Then I will be on course for a slimmer figure Note the words If and Then in the above sentences. You're using conditional logic with those two words: "I will eat the cake on condition that my diet is ruined". Conditional logic is all about that little If word. You can even add Else to it. If I eat the cake Then my diet will be ruined Else If I don't eat the cake Then I will be on course for a slimmer figure And that is what conditional Logic is all about - saying what happens if one condition is met, and what happens if the condition is not met. Visual Basic uses those same words - If, Then, Else for conditional Logic. Let's try it out. Start a new project. Give it any name you like. In the design environment, add a Button to the new form. Double click the button and add the following code to it: Private Sub Button1_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles Button1.Click Dim firstname As String firstname = "Bill" If firstname = "Bill" Then MsgBox("firstname is Bill") End Sub Run the programme and see what happens. You should get a Message Box with the words "firstname is Bill" in it. What we did was to set up a string variable and put the name "Bill" into it. When then used conditional logic to test what was in the variable. In fact, we used an If statement. We said: If the variable called firstname holds the value "Bill" Then display a Message Box We can tidy that up a bit, because a single line of code can get very long with If statements. We can use this format instead. If firstname = "Bill" Then MsgBox "firstname is Bill" End If That's a lot tidier. Note that we start a new line after the word Then. 1. The first line contains our condition: "If the following condition is met". 2. The second line is what we want to do if the condition is indeed met. 3. The third line tells Visual Basic that the If statement ends right here. Try this. Delete the two quotation marks around the word Bill in the If Statement. Your code should now be this: Dim firstname as String firstname = "Bill" If firstname = Bill Then MsgBox "firstname is Bill" End If VB.NET puts a blue wiggly line under Bill. If you try to start your programme, you'll get a message box telling you that there were Build Errors, and asking if you want to continue. Say No to return to the design environment. The reason for the blue wiggly line is that VB insists on you using double quotes to surround you text. No double quotes and VB insists it's not a string of text. Change you code to this. firstname = "Phil" If firstname = "Bill" Then MsgBox "firstname is Bill" Else MsgBox "firstname is not Bill" End If You should have gotten a Message Box popping up saying "firstname is not Bill". The reason is that we included the Else word. We're now saying, "If the condition is met Then display one Message Box. If the condition is not met, display a different Message Box." Notice that the Else word is on a line of it's own. Now, after you have tested your programme, try this. Add a textbox to your form. Then change this line in your code: firstname = "Phil" To this: firstname = Textbox1.Text What the code does is to transfer the text in the Textbox directly to the firstname variable. We can then test what is in the variable with an If statement. When you've finished the code, test it out by typing the word "Bill" (with a capital B) into the textbox, and then clicking the button. Then try it with a lower case "b". So far, we've explored only simple If statements, and we're going to leave it that way for now. But they can get quite complex, because you can have one If statement inside another, and multiple Else statements. The code you have just wrote, however, does demonstrate how you can find out what is in a variable, and take action if the condition is either met or not met. We're now going to explore another way to do that - the Select Case statement. The Select Case statement is another way to test what is inside of a variable. You can use it when you know there is only a limited number of things that could be in the variable. For example, suppose we add another choice for that cream cake. We've only said that the consequences of eating the cream cake is that the Diet will be either "Ruined" or "Not Ruined". But what if we add another option - "Diet Not Tested". In other words, we ate the cake but refused to climb onto the scales to weigh ourselves! With three choices, we can still use an If ... Else statement. But let's change it to a Select Case statement. Remember: all we are doing is testing what is inside a variable, in this case a variable called creamcake. Once we decide what is inside the variable, we can take some action. So let's look at how the Select Case works. Create a Form with a button and a Textbox on it (If you have your form open from the previous section, then you can use this one). Double click the new button. You should see something like this appear. Private Sub Button1_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles Button1.Click End Sub Between the button Sub and End Sub code add the folowing Dim creamcake As String Dim DietState As String creamcake = TextBox1.Text Select Case creamcake Case "Eaten" DietState = "Diet Ruined" Case "Not Eaten" DietState = "Diet Not Ruined" Case Else DietState = "Didn't check" End Select MsgBox DietState Run your code to test it out. Click inside your textbox and enter the word "Eaten". Then click your button to see what happens. Now enter the words "Not Eaten" adn click your button. next, try the word "eaten", with a lowercase "e". So, how does the Select case work? Int he code above, we first set up two variables called creamcake and DietState. Next, we transfer whatever is in Textbox1 to the variable creamcake. The Select Case begins on the next line: Select Case creamcake We tell Visual Basic that we want to start a Select Case statement by simply using the words "Select Case". This is enough to set up the statement. The variable creamcake follows the words Select Case. We're saying, "Set up a Select Case statement to test what is inside the variable called creamcake". The next line is this: Case "Eaten" We ask Visual Basic to check if the variable creamcake contains the word "Eaten". (Is it the Case that ... ?) If it is the Case that creamcake contains the word "Eaten", then VB will drop down to the line or lines of code below and read that. If the variable creamcake doesn't contain the word "Eaten", the programme will skip the line or lines of code below and jump to the next Case. The programme will continue to check all the words after Case to see if one of them contains what is in the variable creamcake. If it finds one, it will read the code below the Case word; if it doesn't find any matches, it will not do anything at all. In our code, we're checking these three Cases: Case "Eaten" Case "Not Eaten" Case Else Note also that it will only look for an exact match - "Eaten", but not "eaten". The next line to examine is this: Case Else You can use the Else word after Case. If the programme hasn't found any matches, it will then execute the code below the Case Else line. The final line to examing is this: End Select So the Select Case checks a variable for any number of different choices. If a match is found, it will then execute code below the Case option it has found. In our code, we've just told the programme to store some text in the DietState variable. After the Select Case statement has ended we displayed the variable in a Message Box. You can use Select Case statement with numbers, as well, and the To word comes in very handy here. If you were checking a variable to see if the number that was in the variable fell within a certain age-range, you could use something like this: Select Case agerange Case 16 To 21 MsgBox “Still Young” Case 50 To 64 MsgBox “Start Lying” End Select Here, a variable called agerange is being tested. It's being checked to see if it falls between certain values. If it does, then a message box is displayed. Exercise Add a new button to your form. Write a programme that tests if a person is a) A teenager, b) in their twenties, c) in their thirties, or d) none of the above. A popular way to use Select Case statements is with a drop down box. You can then test which item a user selected from a list of available items. You're going to write a little programme to do just this. But before you can do so, you'll need to know how to add a Combo Box to a form, and how to get at the values in its list. We'll do that in the next section. Create a new project for this section. Add a button to your new form. Then, locate the Combo Box on the Visual Basic .NET toolbar. It looks like this: Double click the icon to add a Combo Box to your form. Or click once with the left hand mouse button, and then draw one on the form. A combo box is a way to limit the choices your user will have. When a black down-pointing arrow is clicked, a drop down list of items appears. The user can then select one of these options. So let's set it up to do that. • Click on your Combo Box to select it. Then locate the Item property from the Properties Box: • Click the grey button, as above. The one with the three dots in it. When you do, you'll get the following box popping up: • To use the String Collection Editor, type an item and press Return (it's just like a normal textbox. Each item will be one item in your drop-down box.) • Enter five items, as in the image below: • Then click the OK button at the bottom. The Editor will close, and it will look like nothing has happened. However, run your programme and test out your new Combo Box. You should have something like this: You now need to know how to get values from the list. Once you know how to get a value from the list, you can put the value into a variable and test it with some Conditional logic. Getting a value from a Combo Box is fairly straightforward, because it acts just like a Textbox. A Textbox has a Text property, and so does a Combo Box. To get a value from a Textbox, you would code like this MyVariable = Textbox1.Text Whatever is in the Textbox will be transferred to the variable called MyVariable. The process is exactly the same for a Combo Box. The code is like this: MyVariable = Combobox1.Text Now we are transferring whatever is selected from the Combo Box to the variable called MyVariable. Let's try it. Double click the button you added to your form. This will open the code window. Then enter the following code for the button: Dim MyVariable as String MyVariable = Combobox1.Text MsgBox MyVariable Run your programme. When the programme is running, select an item from your Combo Box. Then click your button. Whatever was in the Combo Box window should have ended up in the Message Box. And that's all there is to getting a value from a Combo Box - just access its Text Property and pass it to a variable. Finally, the Combo Box has a DropDownStyle property. Locate this property and you'll notice its value has a drop down box. The box contains three different Combo Box styles to choose from. Experiment with all three and see how they differ. In the next section, we'll take a look at Conditional Operators, what they are, and how to use them. The Conditional Operators allow you to refine what you are testing for. Instead of saying "If X is equal to Y", you can specify whether it's greater than, less than, and a whole lot more. Examine the list of Operators: Operator Meaning > This symbol means Is Greater Than and is used like this: If number > 10 Then MsgBox "The Number was Greater Than 10" End If < This symbol means Is Less Than and is used like this: If number <10 10="" end="" he="" if="" less="" msgbox="" number="" than="" then="" was="">= These symbols mean Is Greater Than or Equal to, and are used like this: If number >= 10 Then MsgBox "The Number was 10 or Greater" End If <= These symbols mean Is Less Than or Equal to, and are used like this: If number <= 10 Then MsgBox "The Number was 10 or Less" End If And You can combine the logical operators with the word And. Like this: If number > 5 And number < 15 Then MsgBox "Greater than 5 And Less than 15" End If Or You can combine the logical operators with the word Or. Like this: If number > 5 Or number < 15 Then MsgBox "Greater than 5 Or Less than 15" End If <> These symbols mean Is Not Equal to, and are used like this: If number1 <> number2 Then MsgBox "number1 is not equal to number2" End If A word about And and Or. Notice the format with And and Or. The variable is repeated twice If VariableName = 7 Or VariableName = 10 Then MsgBox "7 or 10 spotted" If you just put something like this If VariableName > 7 Or < 10 Then MsgBox "7 or 10 spotted" then Visual Basic will give you an error message. What you have to say is If [test the variable for this value] And [test the variable for that value] Then Your If statement can contain an Else part, too. The format is this: If [conditional logic here] Then Some Code here Else Some Other Code here End If But don't worry if all that hasn't sunk in - you'll get used to the Conditional Operators as you go along. In the next part, there's two little programmes for you to write. They will test the skills you have acquired so far. Part 1 - If statements Start a new project. Add a textbox, a Label and a button to your new Form. Then write a programme that does the following: 1. Asks users to enter a number between 10 and 20. 2. The number will be entered into the Textbox. 3. When the Button is clicked, your Visual Basic code will check the number entered in the Textbox. 4. If it is between 10 and 20, then a message will be displayed. 5. The message box will display the number from the Textbox. 6. If the number entered is not between 10 and 20 then the user will be invited to try again, and whatever was entered in the Textbox will be erased Part 2 - Select Case Statements Add a Combo box and another button to your form. Create a list of items for your Combo Box. The list of items in your Combo box can be anything you like - pop groups, football teams, favourite foods, anything of your choice. Then try the following: Use a select case statement to test what a user has chosen from your drop-down list. Give the user a suitable message when the button was clicked. In the next section of this course, we'll move on to loops in Visual Basic .NET. There are three types of loop for us to cover with VB.NET: a For loop, a Do loop, and a While … End While loop. This last one is almost the same as a Do loop, and we won't be covering it here. But the other two types of loop come in very handy, and a lot of the time you can't programme effectively without using loops. What is a Loop? A loop is something that goes round and round and round. If someone told you to move your finger around in a loop, you'd know what to do immediately. In programming, loops go round and round and round, too. In fact, they go round and round until you tell them to stop. You can programme without using loops. But it's an awful lot easier with them. Consider this. You want to add up the numbers 1 to 4: 1 + 2 + 3 + 4. You could do it like this Dim answer As Integer answer = 1 + 2 + 3 + 4 MsgBox answer Fairly simple, you think. And not much code, either. But what if you wanted to add up a thousand numbers? Are you really going to type them all out like that? It's an awful lot of typing. A loop would make life a lot simpler. But don't get hung up too much on the name of the Loop. Just remember what they do: go round and round until you tell them to stop. We'll discuss the For Loop first. his first type of loop we'll look at is called a For Loop. It is the most common type of loop you'll use when you programme. We'll use one to add up our 4 numbers, and then discuss the code. Study the following. In fact, create a new Project. Add a button to your new Form. Double click your new button and type the following code for it: Dim answer As Integer Dim startNumber As Integer answer = 0 For startNumber = 1 To 4 answer = answer + startNumber Next startNumber MsgBox answer Run the programme, and see what happens when you click the button. The number 10 should have been displayed in your message box. The For loop code We start by setting up two integer variables. We set one of these to zero. Then we start our loop code. Let's examine that in more detail. For startNumber = 1 To 4 answer = answer + startNumber Next startNumber We start our loop by telling Visual Basic what type of loop we want to use. In this case it is a For loop: For startNumber = 1 To 4 The next thing you have to do is tell Visual Basic what number you want the loop to start at: For startNumber = 1 To 4 Here we are saying "Start the loop at the number 1". The variable startNumber can be called anything you like. A popular name to call a start loop variable is the letter i ( i = 1). So what we're doing is setting up a variable - the start of the loop variable - and putting 1 into it; Next, you have to Tell Visual Basic what number to end the loop on: For startNumber = 1 To 4 The To word, followed by a number or variable, tells Visual Basic how many times you want the loop to go round and round. We're telling Visual Basic to loop until the startNumber variable equals 4 The command that tells Visual basic to grab the next number in the sequence is this: Next startNumber When Visual Basic reaches this line, it checks to see what is in the variable startNumber. It then adds one to it. In other words, "Get me the next number after the one I've just used." The next thing that happens is that Visual Basic will return to the word For. It returns because it’s in a loop. It needs to know if it can stop looping. To check to see if it can stop looping, it skips the startNumber = 1 part, and then jumps to your end number. In our case, the end number was 4. Because Next startNumber adds one to whatever is in startNumber, then startNumber is now 2 (It was 1 at the start. The next number after one is ... ?). So if startNumber is now 2, can Visual Basic stop looping? No it can’t. Because we’ve told it to loop until it reaches number 4. It’s only reached number 2, so off it goes on another trip around the loop. When the startNumber is greater than the end number, Visual Basic drops out of the loop and continues on it’s way. But remember why we're looping: so that we can execute some code over and over again. To clarify things, change the above code to this: Dim startNumber As Integer For startNumber = 1 To 4 MsgBox("Start Number = " & startNumber) Next startNumber Run the programme, and click your button. What happens? You should have seen this in the message box, one after the other: Start Number = 1 Start Number = 2 Start Number = 3 Start Number =4 Each time round the loop, the code for the message box was executed. You had to click OK four times - startNumber = 1 To 4. Summary So to sum up: 1. A For loop needs a start position and an end position, and all on the same line 2. A For loop also needs a way to get the next number in the loop 3. A loop without any code to execute looks like this: For i = startNumber To endNumber Next i The above code uses two variables for the start and end numbers. The start number for the loop goes directly into the variable called i. When Visual Basic wants the next number, it just add one to whatever is in the variable i. You could use it like this: Dim startNumber As Integer Dim endNumber As Integer Dim i As Integer startNumber = 1 endNumber = 4 For i = startNumber To endNumber Msgbox i Next i Change the code for your button to that new code, and test it out. Study the code so that you understand what is going on. For Loops might not be easier to understand than just typing answer = 1 + 2 + 3 + 4, but they are a lot more powerful if you want to add up a thousand numbers! Exercise Put two textboxes on your form. The first box asks users to enter a start position for a For Loop; the second textbox asks user to enter an end position for the For loop. When a button is clicked, the programme will add up the numbers between the start position and the end position. Display the answer in a message box. You can use this For Loop code For i = startNumber To endNumber answer = answer + i Next i Get the startNumber and endNumber from the textboxes. Exercise Amend your code to check that the user has entered numbers in the textboxes. You will need an If statement to do this. If there's nothing in the textboxes, you can halt the programme with this code Exit Sub For this exercise, you will be passing whatever is in the textboxes to integer variables. It is these variables you are checking with your If Statement. Because numbers will be entered into the textboxes, remember to convert the text to a value with Val( ). But the Text property will return a zero if the box is empty. So your If statement will need to check the variables for a value of zero. If it finds a zero, Then you can use the Exit Sub code. The If statement should come first, before the For Loop code. We saw with the For Loop that a specific number of times to loop was coded into it. We said For startNumber = 1 To 4 We knew that we only wanted to loop four times. But what if we don't know how many times around the loop we want to go? Later, we'll be opening text files and reading the data from them. If we used a For loop to get every line of text, we'd have to know before hand how many lines the text file held. A For Loop would not be very efficient in this case. But a Do Loop would be. With a Do Loop we can use word s like "While" and "Until". And then we can say, "Go round and round the loop While there's still text to be read from the file." An example might make things clearer. Load the form you created for the last exercise, the one that has two textboxes and a Button and tested your understanding of For loops. Add another button to the Form. Your form might look something like this: Double click the new button to open the code window, and then type the following code for the new button: Dim number as Integer number = 1 Do While number < 5 MsgBox number number = number + 1 Loop When you've finished, run the programme and see what happens. The numbers 1 to 4 should have displayed in your message box. So the Do loop keeps going round and around. And when it gets to the top, it tests the "While" part - Do While number is Less Than 5. It's really answering a Yes or No question: is the number inside the variable called number Less Than 5? If it is Less Than 5, go round the loop again. If it's not Less than 5, Visual Basic jumps out of the Loop entirely. You can add the "While ... " part to the bottom, just after the word "Loop". Like this: Do number = number + 1 Loop While number < 5 Try it and see what difference it makes. None, right? But there is a difference between the two. With the "While ... " part at the bottom, the code above it gets executed at least once. With the code on the first line after the word "Do", the code might not get executed at all. After all, the number inside the variable might already be Greater Than 5. If it is, Visual Basic won't execute the code. Do ... Until You have another choice for Do Loops - Do ... Until. There's not much difference between the two, but a Do ... Until works like this. Change your Loop code to the following: Do Until number < 5 MsgBox number number = number + 1 Loop Run the code and see what happens. Nothing happened, right? That's because we "Keep looping UNTIL the number in the variable called number is Less Than 5" The problem is, the number inside the variable is already Less Than 5. And if the number is Less than 5, then the code won't execute - because it has already met the end condition. Change that Less Than sign to a Greater Than sign, and then test your code again. Now what happens? The numbers 1 to 5 should have displayed. Again, the loop keeps going round and around testing to see if our end condition is met, in this case Is Greater Than 5. If the condition is met, VB breaks out of the Loop; if not, keep going round. Change the Greater Than sign to Greater Than or Equal to ( >= ), and test it again. It should now print 1 to 4. The "Until" part can go at the bottom, just after the word Loop. Like this Do MsgBox number number = number + 1 Loop Until number >= 5 To sum up, use a Do Loop if you don't know what the end number is going to be, otherwise a For Loop might be better. You're now going to write a programme that uses a For Loop inside a Do Loop. The programme works out the times table. Start a new project for this. Onto your new Form, place two textboxes and a Button. Set the Text property of Textbox1 to 1, and the Text property of Textbox2 to 10. Set the Text property of the Button to "Go". When the Go button is clicked, the programme will put the numbers from the Textbox into two variables. We'll then put a value into a variable called multiplier. If you're doing the times tables, the format is X multiplied by Y = Z (2 multiplied by 3 = 6) We'll use a Do Loop to work out the multiplier (that's the Y part); a For Loop will work out the rest. We'll then display the results in something called a Listbox. So add a List Box to your form. It looks like this in the toolbox: The form you design should look something like this one: A List box is similar to a Combo Box, in that you have a list of items that the user can select. Here, we're just using it display the results of our programme. We'll add items to the List box with our code, rather than in design time like we did for the Combo box. So, here's the code for the entire programme. Double click your Go button, and add the following: Dim number1 As Integer Dim number2 As Integer Dim multiplier As Integer Dim answer As Integer Dim i As Integer number1 = Val(TextBox1.Text) number2 = Val(TextBox2.Text) multiplier = 2 Do While multiplier < 3 For i = number1 To number2 answer = i * multiplier ListBox1.Items.Add(i & " Times " & multiplier & " = " & answer) Next i multiplier = multiplier + 1 Loop When you've finished, run the programme and see how it works. You should see this appear in your List box: Let's run through the code to see how it works.We'll do that on the next page. Click the As you can see from our last lesson, we've set up five Integer variables - number1, number2, multiplier, answer and i. The next thing we did was to pass whatever is in our two Textboxes straight into the two variable, number1 and number2. The start number goes into textbox one, and the end number goes into textbox2. number1 = Val(TextBox1.Text) number2 = Val(TextBox2.Text) In the next line of code, we set a starting value for the multiplier variable: multiplier = 2 Then we had our two Loops, one inside the other. The first is the Do Loop: Do While multiplier < 3 multiplier = multiplier + 1 Loop This Do loop is exactly the same as the one you met before. All is does is go round and round While the variable called multiplier is Less Than 3. The bit of code between Do and Loop just keeps adding one to whatever is in multiplier (incrementing the variable). The other thing the Do Loop does is to execute our second loop - the For Loop. The For Loop gets executed each time around the Do Loop. The For Loop was this: For i = number1 To number2 answer = i * multiplier ListBox1.Items.Add(i & " Times " & multiplier & " = " & answer) Next i Remember: the number1 and number2 variables hold our numbers from the Textboxes. We set these to 1 and 10. So our first line of the For Loop is really this: For i = 1 To 10 We're saying, "Start a For Loop". Whatever is in the variable called number1, make that the starting number for the Loop. Put this value into the variable called i. The end of the Loop will come when the variable called i has the value 10. Stop looping when you reach this value. The next part of the code reads this: answer = i * multiplier This means, Put into the variable called answer the following sum: whatever is in the variable called i multiplied by whatever is in the variable called multiplier. So that says, put into the variable answer the sum of i times multiplier. We're getting whatever is in i from the For loop. But we're getting whatever is in the variable called multiplier from the Do Loop. So Visual Basic will read the Do While line after noting that the number 2 has been put into the variable called multiplier. It will then check to see if the end of the loop condition has been met - multiplier is Less Than 3. As 2 is not Less Than 2, VB drops down to the next line. The next line is a For Loop - For i = 1 To 10. This entire loop will be executed, and the code inside the For loop worked out. So the For loop gets executed 10 times. Which means that our sum will get executed 10 times. When the end condition of the For loop is met, Visual Basic will exit the For Loop and drop down to the line of code below Next i. The code below Next i is this: multiplier = multiplier + 1 What was inside the variable called multiplier was the number 2, so 2 + 1 = 3. And three is the new number inside the variable multiplier. Then, Visual Basic drops down to the next line, which is Loop. So it goes back up to the Do While line of code Do While multiplier < 3 The same question is asked again: Have we met the end condition for the Do Loop? The end condition was "Keep looping while the variable called multiplier is Less Than 3". Because the value in multiplier is now equal to 3 and not less than 3, the end condition has been met. When the end condition is met, VB exists the Do loop. Exercise Change the Do While line to this: Do While multiplier < 5 Can you guess what will appear in your list box? Run your programme and find out. Finally, a word about the line that displays your text in the list box. It was this: ListBox1.Items.Add(i & " Times " & multiplier & " = " & answer) To add items to a list box with code, first you type the name of your list box: ListBox1 Type a full stop and a drop down list will appear. Select Items from the list. ListBox1.Items Type another full stop and again a drop down list will appear. Select the Add Method ListBox1.Items.Add This method, not surprisingly, lets you add items to your list box. Whatever you want to add goes between a pair of round brackets: ListBox1.Items.Add( ) In between the round brackets, we have this for our code: i & " Times " & multiplier & " = " & answer It might be a bit long, but there are 5 parts to it, all joined together by the concatenate symbol (&): i " Times " multiplier " = " answer The variable i holds the current value of the For Loop; " Times " is just direct text; multiplier holds the value we're multiplying by (our times table); " = " is again direct text; and answer is the answer to our times table sum. If you want to clear the items from a List box you can do this. At the top of the code, enter this line: ListBox1.Items.Clear() So instead of selecting Add from the final drop down list, select Clear. Exercise Add another textbox to your form. This will represent the "times table". So far you have been getting this value directly from the code. For this exercise, get the multiplier value directly from the textbox. Add appropriate labels to all your textboxes. The multiplier variable is the starting point for your "times tables". What else do you need to amend in the code? Think about what happens if you entered a 5 into your new Textbox. If you enter a number 5 or greater, the code doesn't get executed! Can you understand why that is? If not, I suggest you go over this looping section again. Exercise Amend the above code to solve the problem of the programme not being executed. If you successfully solved the problem, what else did you notice? Assuming that you added two labels to your new textboxes - "Start At" and "End At" - what happens if you enter a 3 in the Start At textbox and a 5 in the End At textbox? Will you actually get the 5 times table? What can you do so that the 5 times table is displayed? (Consider using a different Do Loop. What about a Do ... Until loop?) In the next part, we'll take a closer look at the basic Maths symbols you can use in VB .NET. If you're doing any programming, you need to know how to use the basic Math symbols. The basic Math symbols in Visual Basic .NET are these: + The Plus sign adds numbers together - The minus sign takes one number away from another * The symbol above the number 8 on your keyboard tells Visual Basic to multiply two numbers / The forward slash on your keyboard is the divide by symbol = The equals sign A word or two about how to use the mathematical symbols in Visual Basic. You can use the operators by themselves: answer = 8 + 4 answer = 8 - 4 answer = 8 * 4 answer = 8 / 4 Or you can combine them by using parentheses. Here, Visual Basic will work out the sums in parentheses first, and then add the two sums together answer = (8 - 4) + (4 -2) answer = 4 + 2 answer = 6 But you've got to be careful with parentheses, because there is a strict order that VB uses when it's doing maths. Consider this sum answer = 8 - 4 + 4 + 2 * 2 Try that code behind a new button. Display the result in a MsgBox. What answer did you get? 12! It's wrong! But why? You would think it would work out the sum like we do - left to right 8 - 4 = 4 + 4 = 8 + 2 = 10 * 2 = 20 But VB doesn't work it out like that. Visual basic will do the multiplying first. So it will calculate like this 2 * 2 = 4 8 - 4 + 4 = 8 8 + 4 = 12 To make sure Visual Basic does your sums correctly you have to be careful of the parentheses. Try changing the code to this: answer = (8 - 4) + (4 + 2) * 2 Now what happens. That's right - you get 16! It's still wrong! At least it is if you are working from left to right. But Visual Basic isn't. It will do the (4 + 2) * 2 part first, and then add that to 8 - 4. Which gives you 16. In order to force Visual Basic to get the sum right, you need even more parentheses. Try this code and see what happens: answer= ((8 - 4) + (4 + 2)) * 2 Finally we get the answer we've been expecting - 20! The parentheses above have grouped our sums into separate sections, thereby forcing VB to do the sums in the right order. So take care when using parentheses to do your sums: the order that Visual Basic does its sums does matter! In the next section of the course, we'll have some fun adding menus to a Visual basic .NET form. In this section we’ll see how to add menus to a Visual Basic .NET form. These type of menus are very common to Windows programme. Visual Basic itself has many of these drop down menus - File, Edit, View, Project, Format, etc. And they’re very easy to add. Start a new project. To your new form, use the toolbox to add a MenuStrip control: Double click the control to add one to your form. When you do, you'll notice two things. At the top of your form, you'll see this: We'll see how to construct our menu soon. But notice the other things that gets added to your project. Examine the bottom of your screen, on the left. You'll see this: This is the control itself. If you click on this (it's highlighted above), you'll see that the Properties box on the right changes. There are many properties for the control. But there are lots of properties for the MenuItem object. The MenuItem object is the one at the top of the form - The one that says Type Here. To start building your menu, click inside the area that says "Type Here". Type the word File: Now press the enter key on your keyboard. Your menu will look like this: To create items on your File menu, click inside the Type Here box. Enter the word New, and press the enter key on your keyboard again. Your menu will then look like this: Add an "Open" and a "Save" item to your menu in the same way. It should look like this: The final item we'll add to our menu is an "Exit" item. But you can add a separator between the "Save" and "Exit". To add a separator, click inside the blue "Type Here" box. Instead of typing a letter, type the minus character "-" (in between the "0" key and the "+/=" key on your keyboard). When you hit your return key, you'll see the separator appear: Click inside the "Type Here" area, and add an Exit (or Quit) item. Click back on your form, away from the menu, to finish off. You should now have a File menu like this one: To see what your menu look like, Run your programme. Click the File menu. We haven't added any code to the menu yet, so nothing will happen if you click an item on the menu. But it does look quite good. Very professional! Stop your programme and return to the design environment. Click File in Design Time to see your drop down menu. You can double click an item to open up the code window. But don't do that yet. Another way to get to the code for an object is this: • Press F7 on your keyboard to go to the code window • Click the black arrow at the top, where it says General: The Exit menu here is "ExitToolStripMenuItem". If you were to click that item, a code stub would open, ready for you to type your code. However, "ExitToolStripMenuItem" is very difficult to remember. We can rename our menu items so that they are more descriptive. So do this: • Get back to your form by pressing Shift + F7 on your keyboard • Click the File menu to select it • Select your Exit (or your Quit) item (Careful not to click in the middle as this may open the code window.Click near the left edge somewhere.) • When you have the Exit item selected, look at the properties box on the right: • Click inside the Name property • Change it to mnuExit (or mnuQuit) • Press your return key on your keyboard to confirm the change Now press F7 again to bring the code window up. Click the drop down arrow of the General box, and you should see the new name appear (Notice that MenuItem6 has vanished): Click on your new mnuExit item. Nothing will happen! To jump straight to the code, you need to look at the drop down box opposite. It will probably say "Declarations". Click the arrow and you'll see a new list: The items in the Declarations box are called Events. The Event you want is the Click event. So select that one from the list (we'll cover Events in more depth later). When you select Click from the list, you are taken straight into the code for that event. It should be like this one: The code above has been tidied up to fit on this page; yours will all be on one line. But notice that it says mnuExit_Click. Don't worry too much about what it all means; we'll get to that in a later section. What we want to do is add some of our own code, so that out Exit menu item actually does something. There's only one line of code to add. It's this: Me.Close( ) The word "Me" refers to the form. When your type the word Me, you'll see a list if items appear. Double click the word Close, then press your return key. Your code window should look like this: (Again this has been tidied up to fit on this page.) To test out your new code, run your programme. Click your File menu, and then click the Exit item. Your form should close down, and you'll be returned to the design environment. A sub menu is one that branches of a menu item. They usually have an arrow to indicate that there's an extra menu available. You will have seen these plenty of times in Windows programmes. You can create our own sub menus quite easily. Try this: • Return to the Form view (Shift + F7 is a shortcut) • Click on your File menu so that you can see it all • Select the New item (Careful where you click. Click once on the left edge). You should see this: • Click on the "Type Here" just to the right of New • You'll see yet more "Type Here" areas: • Type New Project, and then hit the return key on your keyboard • Type in New File and then click away from the menu, somewhere on the form • You will then have a menu like this one: • Save your work, and then run your programme. Click your new menu to see the following: Of course, none of the menu items work except the Exit menu. But you should have found that adding menus to your programmes is an easy matter with VB.NET. One more thing we can do. If you look closely at a lot of menu items, you see that they have shortcuts attached. There's two types of shortcuts: An underline shortcut, and a key combination shortcut. We'll see how to do that in the next section. Underline Shortcut To add an underline, do this: • Click on your New menu item once. This will select it • Position your cursor before the "N" of New • Type an ampersand symbol (&) • Hit the return key on your keyboard • You should see this: Notice that "N" of New is now underlined. If you want an underline shortcut, the ampersand character should be typed before the letter you want underlined. Add underlines for the "F" of you File menu, the "O" of Open, the "S" of Save, and the "X" of Exit. When you're done, your menu should look like this one: Time to see if your shortcut works. Run your programme. To use the underline shortcuts on menus, you first hold down the Alt key on your keyboard. Then type the underline character. • Hold down the Alt key while your programme is running (You might not be able to see the underlines until you press the Alt key.) • Press the letter "F" on your keyboard • Then press the letter "X" (for the Exit menu) • Your programme should close down All that and you didn't have to write a single line of code! Key combination shortcuts A key combination shortcut is one that appears at the end of a menu item (Ctrl + X, for example). You can easily add this option to your own programmes. So try this: • In Design time, select the Exit item on your menu • Look at the properties box on the right • Locate the ShortcutKeys item: • Click the down arrow to reveal the following: The Modifier is the key you press with your shortcut. For example, the CTRL key then the "X" key on your keyboard. Place a check inside the Ctrl box. Then select the letter "X" from the Key dropdown list, as in the next image: Click back on your menu to see what it looks like: Run your programme and test out the shortcut. Don't click the File menu. Just hold down the Ctrl key on your keyboard. Then press the letter X. Again, the programme will close down. You can add these types of shortcuts to any menu item. Just remember to choose a different key stroke combination for each one. And don't have too many of them - they'll spoil the look of your menu! Now that you know how to add Menus, Sub Menus and Shortcuts it's time for you to complete your own menu bar. Click the project below to see what you need to do. It's not very difficult! In the section after the project, you'll see how to add code for your new menu bar. Add the following Main Menu items to the menu bar you have already designed in this section: 1. Edit 2. View On your Edit Menu, place the following menu items: • Undo • Cut • Copy • Paste On your View Menu, place the following menu items: • View Textboxes • View Labels • View Image Just like you did with the Exit menu item, Change the Name property of ALL menu items. Do not leave them on the defaults of "MenuItem1", "MenuItem2", etc. (You should change the Name property to something relevant, and use the prefix mnu. For example, the Undo item could have the Name mnuUndo.) • Add an underline shortcut for ALL menu item • Add a least one key combination shortcuts per drop down menu (you already have one on the File menu, so this doesn't count) When you have finished, your menus should look like these (though you can use different key combinations, if you like): Edit Menu View Menu • Write code to display a message box whenever a menu item is clicked, or its shortcut used. The message box should explain what the menu item will do when it's fully implemented. There's only one line of code to write for each menu item. You can get at the code for the click event of each menu item in exactly the same way that you did for the Exit menu item. In the next part, you'll learn how to write code for all your new menu items. We start with the Open menu item. For the last project, you designed a form interface that had a File, Edit and a View menu. In this section, we'll write code so that your menu items actually do something other than displaying message boxes. In other words, the Edit > Cut menu will really cut text, and the Edit > Paste menu will really paste text. So open up the project you completed for the previous section. Comment out or delete any message box code. (You comment out code by typing a single quote character at the start of the line. The line will then turn green, and will be ignored when the programme is run.) We'll start with the File > Open menu. The Open File Dialogue Box In most programmes, if you click the File menu, and select the Open item, a dialogue box is displayed. From the dialogue box, you can click on a file to select it, then click the Open button. The file you clicked on is then opened up. We'll see how to do that from our menu. (Except, the file won't open yet - only the dialogue box will display, and then name of the chosen file. You'll learn how to open files in a later section.) First, place two textboxes on your form. In the properties box, locate the MultiLine property. It is set to False by default (which is why you can't change the height of textboxes). Change this value to True. Type some default text for the Text Property of textbox1. Change the Font size to 14 points. Your form should now look something like this one: We'll work with these textboxes when we do the Edit menu. So let's leave them for now. When we click on File > Open from our menu, we want the Open dialogue box to appear. This is fairly straightforward in VB.NET. In fact there is even a control for it! Open up your toolbox, and locate the control called "OpenFileDialog". You might have to scroll down to see it. But you're looking for this: Double click the control to add one to your project. But notice that the control doesn't get added to your form. It gets added to the area at the bottom, next to your menu control: The shaded area surrounding the control means that it is selected. If you look on your right, you'll see the properties that you can use with the control. Click on the Name property and change the name to openFD. When you change the name in the properties box, the name of the control at the bottom will change: We’ll now write some code to manipulate the properties of our new control. So do the following: • Access the code for your File > Open menu item. (To do this quickly, you can simply double click the Open item on your menu bar. Or, press F7 to access the Code View.) • Click the name of your menu item from the left drop down box at the top of the code • Then select the Click event from the drop down box to the right • Your empty code should be this (the code below has underscore characters added, so that it can fit on this page): Private Sub mnuOpen_Click(ByVal sender As Object, _ ByVal e As System.EventArgs) _ Handles mnuOpen.Click End Sub With you cursor flashing between the two lines of your code, add the following: openFD.ShowDialog() When you typed a full stop after the openFD, you probably saw a list box appear. You can just double click the ShowDialog() item to add it to your code. But this method of the OpenFileDialog control does what you'd expect it to do: Shows the dialogue box. You can even test it out right now. Press F5 to run your programme. Then click the Open item on your File menu. You should see an Open dialogue box display. Return to the design environment, and we'll explore some more things you can do with this Dialogue box control. The Initial Directory You can set which directory the dialogue box should display when it appears. Instead of it displaying the contents of the "My Documents" folder, for example, you can have it display the contents of any folder. This done with the Initial Directory property. Amend your code to this: openFD.InitialDirectory = "C:\" openFD.ShowDialog() Run your programme again, and see the results in action. You should see the contents of the "C" folder on your hard drive (if you root folder is called something else, change the code above). The Title Property By default, the dialogue box will display the word "Open" as a caption at the top of your dialogue box. You can change this with the Title property. Add the line in Bold to your code: openFD.InitialDirectory = "C:\" openFD.Title = "Open a Text File" openFD.ShowDialog() Run your code again, and Click File > Open from your menu. You should see this at the top of the Open dialogue box: In the next parts of this tutorial, we'll see how to change the Filter property, and how you can select a file from the list. In the previous section, we saw how to add an Open File Dialogue to our menus. We then saw how to add an Initial Directory and a Title property. In this section, we'll learn about the Filter property. The Filter Property In most dialogue boxes, you can display a list of specific files that can be opened. These are displayed in the "Files of Type" drop down list. To do this in VB.NET, you access the Filter property. We'll restrict our users to only opening Text files, those that end in the extension ".txt". The following code (in bold) shows how to use the filter property: openFD.InitialDirectory = "C:\" openFD.Title = "Open a Text File" openFD.Filter = "Text Files|*.txt" openFD.ShowDialog() Run your code. Click File > Open on your menu, and then click the arrow on the drop down box for "Files of Type". You should see this: You can add a little bit extra to the description part of the filter, if you like. This will server a s a reminder of just what the extension is. Try amending the line to this: openFD.Filter = "Text Files(*.txt)|*.txt" When you run your code, you see this in the Files of Type area: If you scroll across your Open dialogue box, you should see only text files displayed (you'll still see folders). If you can't see any files at all, double click a folder and explore. You'll soon see something like this: To display files of more than one type, add a Pipe character between each filter. In the code below, two file types are specified, text files and Microsoft Word documents: openFD.Filter = "Text Files|*.txt|Word Files|*.doc" When the programme is run, you should be able to see two file types in the list: In the next section, we'll see how to return which file was selected by the user. You'll notice from the previous section that if you select a file and click the Open button, nothing happens. That's because the Open dialogue boxes doesn't actually open files! It only displays a list of files that CAN be opened, if you were clever enough to write the code. We'll be writing the code that does the opening (and the saving) in a later section. But you need to be able to get the name of the file. The Open Dialogue box has a property that returns the file name that was selected. Not surprisingly, it's called FileName: OpenFD.FileName However, this is a property that returns a value (a string value). The value is the name of a file. So you have to assign this value to something. We can assign it to a new variable: Dim strFileName As String strFileName = OpenFD.FileName The value in the variable strFileName will then hold the name of the file selected. So change you code to this (new lines in bold): Dim strFileName As String openFD.InitialDirectory = "C:\" openFD.Title = "Open a Text File" openFD.Filter = "Text Files|*.txt" openFD.ShowDialog() strFileName = OpenFD.FileName MsgBox strFileName Run your programme, and click your File > Open menu. Navigate to where you have some text files. Click one to select it. Then click the Open button. You should see the name of the file displayed in your message box: Notice that the location (the path) of the file is also displayed. One thing you may have noticed is that if you select a file, then click the Cancel button, the message box still displays. But it will be blank. In your code, you will only want to do something with a file if the Cancel button is NOT clicked. You can test to see if it was clicked by assigning the openFD.ShowDialog() to an integer: Dim DidWork As Integer = openFD.ShowDialog() You can then test what is inside of the DidWork variable. If the cancel button is clicked, the result of the action is stored by VB.NET in this property: DialogResult.Cancel You can compare the two in an if statement: If DidWork = DialogResult.Cancel Then MsgBox("Cancel Button Clicked") Else strFileName = openFD.FileName MsgBox(strFileName) End If In the code above, you're only opening the file if the Open button was clicked. The code is a bit more complicated, but study it for a while and it will make sense! In the next part, we'll take a look at how to code for the Save menu. The save dialogue box works in the same way as the Open dialogue box. However, you can't use the same control. If you examine the Toolbox, you'll see a control called SaveFileDialog: Double click this control to add one to your project. If you look at the bottom of the screen, you'll see the control added there, rather than onto your form: In the image above, the control is selected. Changed the Name property of your control to something more manageable. Change it to saveFD. (You learned how to do this in a previous section.) Access the code for your File > Save menu item. Then add the following code: saveFD.ShowDialog() Your code window should look like this one (Again, underscores have been added to the first line to fit on this page): Run your programme, then click your File > Save menu item. You should see the Save As dialogue box appear. Just like the Open control, you can use the properties of the Save control on your dialogue boxes. Try changing these properties, just like you did with the Open properties: Initial Directory Title Filter FileName There's another useful property you can use with the Save control - the Overwrite prompt. When you set this property, a message box pops up warning you that the file will be overwritten, and do you want to continue. To use this property, the code is this: saveFD.OverwritePrompt = True However, just like the Open box, when you click the Save button no file is actually being saved. You have to write your own code for this. You'll learn how to do this in a later section. For now, let's move on to the Edit menu. If you haven't already, add two textboxes to your form and set their MultiLine property to True. What we'll do now is to get the following menu items to work: Undo, Cut, Copy and Paste. We'll start with Copying: The Copy Menu If you type Textbox1 in your code window, then a full stop, you get a list of properties and methods available to the textbox. Scroll up to the top and locate the Copy method: Notice the tool tip in yellow. It's telling you what this method does - copies the current selection to the clipboard. The clipboard is a temporary storage area available to most Windows applications. When you invoke the Copy method of the textbox, any selected text is place in this temporary storage area for you. You don't have to write any other code. So access the code for your Copy menu item, and add this line to it: Textbox1.Copy() Your code window should look something like this: That's all there is for the copy menu! But nothing visible will happen when you run your code. Let's paste it into the second textbox. The Paste Menu Again, there's only one line of code to write. It's this: TextBox2.Paste() Notice that we're saying paste to textbox2. Because the copy menu places the text from textbox one onto the clipboard, you only need this one line of code. You're saying "Whatever is on the Clipboard, paste it into Textbox2". So add that line to your Paste menu item. Your code window should look like this: Time to test it out. Run your programme. Select all the text in textbox one (it might already be selected), then click Edit > Copy from your menu. Click inside the second textbox. Then click Edit > Paste from your menu. The text should appear in textbox two. The Cut Menu Access the code for you Cut menu item. Add the following code to it: TextBox1.Cut() Run your programme, and select the text in textbox one. From your menu, click Edit > Cut. The text should disappear (it's on the clipboard, though). Click inside textbox two, and click Edit > Paste. The text should be pasted over. The Undo Menu For the Undo menu, add this line of code: TextBox1.Undo() Run your programme. Then select the text in textbox one. Click Edit > Cut and the text disappears. Now click Edit > Undo. The text reappears. The Edit menu we implemented is only a simple one. But it does demonstrate what you can do with VB.NET and menus. We'll completed out look at menus by coding for the View menu you added to your form. In the process, we'll take a look at pictures boxes, as well as seeing how easy it is to hide and disable controls on a form. The items on our view menu are: View Textboxes View Labels View Images Although these are not terribly practical examples of what to place on a View menu, they will help us to demonstrate a few useful techniques. The first of these is how to show and hide controls. The View Textboxes menu item Controls on a form can be hidden or shown as the need arises. The process is quite easy. Access the code for your View Textboxes menu item. Type the following for the menu item: Textbox1.Visible = False Textbox2.Visible = False Run your code and test it out. Click View > View Textboxes. The two textboxes you added should disappear. To hide a control, simply set it's Visible property to False. If you want to get it back, show a control by setting the Visible property to True. A good idea is to have the ability to toggle a control on and off: One click of a menu item could hide the control, and a second click could show it again. You can do that with your menus. Each item on your menu has a Checked property. If set to True, you'll see a tick appear next to the menu item. As in the image below: You can use this Checked property as a toggle: If the menu item is ticked, display the textbox; if it's not ticked, hide the textbox. Delete or comment out the line of code for your View Textboxes menu item. Add the following line in its place (this assumes that you've Named your View Textboxes menu item as mnuViewTextboxes. If you've named it something else, changed the part before the full stop): mnuViewTextboxes.Checked = Not mnuViewTextboxes.Checked This line toggles the Tick on and off. The part before the equals sign sets the Checked property of our menu item. The part after the equals sign sets it to whatever it's NOT at the moment. So if Checked is True, it's NOT False. In which case, set it to False. Run your code and test it out. Click View > View Textboxes. Have a look at the menu again, and you'll see a tick appear. Click View > View Textboxes again and the tick will disappear. We can show the textboxes if there's a tick next to View Textboxes. Just test the value of the Checked property in an If Statement. Add this If Statement just below your first line: If mnuViewTextboxes.Checked = True Then TextBox1.Visible = True TextBox2.Visible = True Else TextBox1.Visible = False TextBox2.Visible = False End If So the If Statement examines the Checked property of the menu item. If it's True, make the textboxes Visible ; Else, we set the Visible property of the textboxes to False. Before you run your code, return to the Form view by holding Shift + F7 on your keyboard. When you have your form displayed, and not the code, click on textbox1 to select it. In the property box, locate the Visible property and set it to False. Do the same for texbox2. When your form runs, the two textboxes will then be hidden. Now run your programme and test out your new menu. Click View > View Textboxes and see if they toggle on and off. Exercise Add two labels to your form. Write code to toggle the labels on and off. The two labels should disappear with the textboxes. And they should reappear when the menu item is toggled to the on position In the next part, we'll see how we can insert images. We'll use the View Images menu for that. It's easy to add an image to your form with VB.Net. To insert an image, locate the Picture control in the toolbox. Either double click the control, or hold down your mouse on the form and draw one out. You should see something like this: Change the Height and Width properties of the Picture Box to 100, 100. You'll have a small square. To make it stand out more, locate the BorderStyle property. Change the value to Fixed3D. Your Picture Box will then look like this: To add a picture at design time, locate the Image property in the properties box: Download and unzip the image at the top of the page. Then click the button with the three dots on it. A dialogue box appears. Locate an image. Select it, and then click Open in the dialogue box. The image will appear in your Picture Box: If you select an image that is too big for the picture box, only part if it will be visible. The Picture Box control does not resize your image. You can, however, set another property of the picture box - the SizeMode property. Set this to AutoSize and your picture box will resize to the size of your image. Insert an Image with your View Menu You can use your open file dialogue box again to specify an image for the user to select. We'll do this from the View Images menu item. Highlight you code for the mnuOpen item. (If you haven't yet coded for the File > Open menu item, click here.) Copy the first five lines, these lines: Dim strFileName As String openFD.InitialDirectory = "C:\" openFD.Title = "Open an Text File" openFD.Filter = "Text Files|*.txt" Dim DidWork As Integer = openFD.ShowDialog() Paste them to your mnuViewImages menu item code. Change the Title property to this: openFD.Title = "Open an Image" And change the Filter property to this: openFD.Filter = "jpegs|*.jpg|gifs|*.gif|Bitmaps|*.bmp" Run your code and click your View Images menu item. You should see the Open dialogue box appear. If you look at the "Files of type" box, you should see this: You should now be able to see only the three image formats we've specified. To insert an image into your Picture Box, some new code is needed. Again though, we'll wrap it up in an If Statement. Add the following code below the lines you've just added: If DidWork <> DialogResult.Cancel Then strFileName = openFD.FileName PictureBox1.Image = Image.FromFile(strFileName) openFD.Reset() End If There's only two lines you haven't met yet. The first is this line: PictureBox1.Image = Image.FromFile(strFileName) Previously, you were loading the image into the Image property of PictureBox1 directly from the Properties Box (by clicking the grey button with the three dots in it). Here, we're loading an image into the Image property using code. The way you do it is with the FromFile method of the Image Class. Although that might be a bit baffling at this stage of your programming career, all it means is that there is some in-built code that allows you to load images from a file. In between round brackets, you type the name and path of the file you're trying to load. Since our file name has been placed inside of the strFileName variable, we can just use this. You can then assign this to the Image property of a Picture Box. The last line, openFD.Reset(), will reset the initial directory of the open file dialogue box. To see what this does, comment out the line (put a single quote at the start of the line). Run your programme and Click View > View Images. Insert an image and then click File > Open. You'll notice that the files displayed in your dialogue are from the last directory you opened, rather than the one you set with "InitialDirectory = "C:\". By resetting the open dialogue box control, you're fixing this problem. OK, that concludes our look at menus. We'll create a new programme now, and explore checkboxes, radio buttons and Group Boxes. wo more useful controls in the Visual Basic toolbox are the Check box and the Option Button. You use these when you want to give your users a choice of options. We'll add both of these to a new Form, and then combine them with a Select Case statement to read what the user has chosen. Check Boxes So start a new project. Locate the Checkbox control in the toolbox. Double click the control and a Checkbox appears on your new Form You'll see that the Checkbox has the Text property of CheckBox1 by default, and a Name of CheckBox1. If you were to double click again on the Checkbox icon in the toolbox, the new control would be called CheckBox2. The problem with this approach is that by double clicking each Checkbox, you have several individual Checkboxes. And if you wanted to move them around you'd have to move each Checkbox separately. There is a way to group all your Check Boxes together, and move them around as one - by using a Group Box. (You can use a Panel control as well, but we'll stick with the Group Box.) So, click on your Checkbox with the right mouse button. From the menu that pops up, select delete to get rid of it. Now locate the Group Box control in the toolbox: It's better to draw this one on the form, rather than dragging and dropping. When you've added one, the only thing you should have on your Form is a Group Box. We're not going to be using many of the Properties in the Group Box Property box. But click on your Group Box to select it, and change to the Text Property to "Soaps". Change the Font Property to anything you like. You should now have a Form like this one The Group Box we just added will hold our Checkboxes. It acts as a container for the controls. To move the Checkboxes about, we can just click on the Group Box to select it, and drag and drop the Group Box somewhere else. The Checkboxes will all move with the Group Box. Let's add some Checkboxes to it. You CAN'T double click a checkbox and add it to a Group Box. The only way to add a control to a Group Box is to draw one on the Group Box. 1. Click once with your left mouse button on the Checkbox icon in the VB toolbox 2. Move your mouse pointer over to the inside of the Group Box. The mouse pointer will change to a cross 3. Hold down you left mouse button inside the Group Box. Keep the button held down, and drag outwards. Release the left button when you're happy with the size. You can always resize it later. 4. Add 5 Checkboxes to your Group Box 5. Change the Text property of each of your Checkboxes to any five Soap Operas. Your Form should now look something like the one below: Run your programme to test it out. Click inside a Checkbox to select an item. Click again to deselect it. When you've finished, return to the Design Environment and click on the Group Box itself to select it. Make sure the Group Box IS selected, and not one of your Checkboxes. You can now drag the Group Box around your Form and all the Checkboxes will move with it. The point about having Checkboxes is to offer your users multiple choices. We'll now write some code to get the choices made by the user. All the Checkboxes with ticks inside them will have their Text displayed in a Message Box. We'll do that in the next part of this tutorial. f you click on any one of your Checkboxes and examine its Properties in the Property box, you'll notice that it has a CheckState Property. Click the down arrow to see the options this CheckState has. As you can see, you are given three options: Unchecked, Checked, Indeterminate. If a checkbox has been selected, the value for the CheckState property will be 1; if it hasn't been selected, the value is zero. (The value for the Indeterminate option is also zero, but we won't be using this.) We're only going to test for 0 or 1, Checked or Unchecked. You can do the testing with a simple If Statement. Like this: If CheckBox1.CheckState = 1 Then MsgBox("Checked") End If After you type the equal sign, though, VB will give you a drop down box of the values you can choose from. So the above code is the same as this: If CheckBox1.CheckState = CheckState.Checked Then MsgBox("Checked") End If Whichever you choose, the Statement will be True if the checkbox is ticked and False if it isn't. Add a Button to your Form and put that code behind it (either of the two, or test both). When you've finished typing the code, run your programme. Put a tick inside Checkbox1, and click your button. You should get a Message Box popping up. Amend your code to this: If CheckBox1.CheckState = CheckState.Checked Then MsgBox("Checked") Else MsgBox("Not Checked") End If An alternative to Else is ElseIf. It works like this: If CheckBox1. CheckState = 1 Then MsgBox "Checked" ElseIf Checkbox1. CheckState = 0 Then MsgBox "Unchecked" End If When using the ElseIf clause, you need to put what you are testing for on the same line, just after ElseIf. You put the word Then right at the end of the line. You can have as many ElseIf clauses as you want. In other words, it's exactly the same as the first "If" line only with the word "Else" in front "If". Add 4 more If Statements to check for the values in your other Checkboxes : Checkbox2.CheckState, Checkbox3.CheckState, etc. We're now going to get rid of the Message Boxes inside the If Statements. So either comment out all your MsgBox lines, or delete them altogether. Instead, we'll build up a String Variable. So add a String Variable to the code for your button, and call it message. The message variable needs to go inside the If Statement. If the user has checked a Box (If its CheckState property is 1), then we build the message. We need to remember what is inside the message variable, so we can just use this: message = message & Checkbox1.Text & vbNewLine That way, every time an option is Checked, Visual Basic will keep what is in the variable called message and add to it whatever the text is for the Checkbox. So add that line to your If Statements. Something like this If Checkbox1.CheckState = 1 Then message = message & Checkbox1.Text & vbNewLine End If If Checkbox2.CheckState = 1 Then message = message & Checkbox2.Text & vbNewLine End If And at the end of your If Statements, on a new line, add this: MsgBox "You have chosen " & vbNewLine & message Here, we're building a text message for out Message Box. We're saying our Message Box is to contain the text "You have chosen " And a New Line And whatever is inside the variable called message. When you've finished, Run your Programme to test it out. Put a tick inside all of your Checkboxes. When you click your button all your Soap Operas should appear in the Message Box. Check and Uncheck some options, and click the button again. Only those items that are selected should appear in your Checkbox. So, we can test to see which Check Boxes a user has ticked, and we can keep a record of those choices for ourselves. What we can also do is count how many Check Boxes were ticked. We can then use a Select Case Statement to display a suitable message. Keeping a count is straightforward. First we set up an integer variable called counter, and set it's value to zero. Dim counter As Integer = 0 Then we can just keep adding one to whatever is in this counter variable. In other words, every time a Checkbox has a value of 1 (is ticked), we can add one to our counter (increment our variable). We can add this straight into our If Statement, on a new line after the message code. counter = counter + 1 So your code would be this: If Checkbox1.CheckState = 1 Then message = message & Checkbox1.Text & vbNewLine counter = counter + 1 End If To test that your counter is working, you can add a second message box to the end of the code, just below your first message box: MsgBox("Counter = " & counter) Or adapt your first message box: MsgBox("You have chosen " & counter & " soaps") Now that we have a way to count how many Checkboxes are ticked, we can add a Select Case Statement. Exercise Add a Select Case Statement to the end of your code to test whatever is inside the variable called counter. Remember what the format is for a Select Case? It's this: Select Case VariableName Case 0 MsgBox "You obviously don't watch soaps!" End Select If you have 5 Check Boxes on your Form, then the maximum value that counter will hold is 5. So you only need to go up to Case 5. Add suitable messages for each Case that you're testing for. This has been quite a long lesson, so give yourself a big pat on theback if you got through it! In the next part, we'll see how to add Option Buttons to a VB .NET form. Radio Buttons, sometimes called Option Buttons, are used when you want to restrict a user's choice to one, Male/Female, for example. A Checkbox would be no good here, because a user could tick both boxes. You want to force your users to pick only one from your list of options. Adding Radio Buttons to a Form is exactly the same process as adding a Checkbox. Again, we'll add some Radio Buttons to a Group Box, and write code to extract what the user has chosen. 1. Add a Group Box to your Form. 2. Set the Text Property of the Group Box to "Best Sit Com of all time" 3. Set the Font options to anything you like 4. Place five Radio Buttons into your Group Box (By default, they'll be called "Option1", "Option2", "Option3", etc 5. Set the Text Property of the Five Radio Buttons to Only Fools and Horses, Dad's Army, Blackadder, Fawlty Towers, Vicar of Dibley 6. Your Form should now look something like this: Run your programme and test to see if you can indeed only select one item from the list. The reason you can only select one is that all the radio buttons are placed in the same group box. You can place another set of radio buttons in a second group box, and these would work independently of the set of radio buttons in the first group box. To test which Sit Com was chosen, you can use an If … Elseif Statement. You can do this because only one of the radio buttons will be True if selected: all the others will then have a value of False. So place a Button on your form. Set the Text property to something appropriate. Then double click your new button to open up the code window. Type the following code (Notice that the Property is now Checked, and not CheckState): Dim ChosenSitCom As String If RadioButton1.Checked = True Then ChosenSitCom = RadioButton1.Text ElseIf RadioButton2.Checked = True Then ChosenSitCom = RadioButton2.Text ElseIf RadioButton3.Checked = True Then ChosenSitCom = RadioButton3.Text ElseIf RadioButton4.Checked = True Then ChosenSitCom = RadioButton4.Text ElseIf RadioButton5.Checked = True Then ChosenSitCom = RadioButton5.Text End If MsgBox("You voted for " & ChosenSitCom) By using If … ElseIf we can check which radio button a user selected. The Text property from the chosen radio button is then placed in a String variable called ChosenSitCom. At the end, we then display the selected radio button in a message box. Run your programme and test it out. Select a Sit Com, and then click your Button. You should see the item you selected displayed: Exercise Add a Textbox to your Form. Write code to transfer a chosen Sit Com to the Textbox when the button is clicked. Add a label next to the Textbox with the Caption "You Voted For. . . " And that's all there is to adding Option Buttons to your VB .NET forms. In the next section of the course, we'll take a look at error checking. Error handling debugging your code is something you will need to do. Unless you write perfect code every time, there's no getting away from it. In this section, we'll take a look at ways you can track down errors using VB.NET. Types of Error Programming errors are generally broken down into three types: Design-time, Runtime, and Logic errors. A Design-time error is also known as a syntax error. These occur when the environment you're programming in doesn't understand your code. These are easy to track down in VB.NET, because you get a blue wiggly line pointing them out. If you try to run the programme, you'll get a dialogue box popping up telling you that there were Build errors. Runtime errors are a lot harder to track down. As their name suggests, these errors occur when the programme is running. They happen when your programme tries to do something it shouldn't be doing. An example is trying to access a file that doesn't exist. Runtime errors usually cause your programme to crash. If and when that happens, you get the blame. After all, you're the programmer, and you should write code to trap runtime errors. If you're trying to open a database in a specific location, and the database has been moved, a Runtime error will occur. It's your job to predict a thing like this, and code accordingly. Logic errors also occur when the programme is running. They happen when your code doesn't quite behave the way you thought it would. A classic example is creating an infinite loop of the type "Do While x is greater than 10". If x is always going to be greater than 10, then the loop has no way to exit, and just keeps going round and round. Logic errors tend not to crash your programme. But they will ensure that it doesn't work properly. Design time errors, remember, are syntax errors. It's when VB .NET hasn't understood what you have typed. If that isn't clear, a few examples should explain it beter. So do the following: • Create a new Windows project • Add a button and textbox to your form • Leave the Name properties on the defaults of Button1 and Textbox1 • Double click your button to access its code, and type the following: Textbox2.Text = "Debug" When you finish typing the line, VB.NET puts a blue wiggly line under Textbox2: If you hold your mouse over Textbox2, you'll see a yellow tool tip appear, like the following: The error is occurring because you don't have a textbox called Textbox2. You'll also see this same "Not declared" error if you try to set up a variable on the fly (which you were allowed to do in previous version of VB.) As an example, change your code to this: strText = "Debug" TextBox1.Text = strText Here, we're trying to put the word "Debug" into a variable called strText. We then want to assign this variable to the Text property of Textbox1. However, VB.NET protests about this, and puts a wiggly line under all occurrences of strText: Hold your mouse over the variable strText and you'll see the "not declared" tip again: The problem this time is that we haven't declared the variable strText. Change the code to this: Dim strText As String strText = "Debug" TextBox1.Text = strText Now that we have declared a variable, the wiggly lines will go away. If we added the variable declaration in the wrong place, however, the wiggly lines would come back. Change you code to this: strText = "Debug" TextBox1.Text = strText Dim strText As String The wiggly lines will be back. That's because the declaration comes on the third line. When VB.NET meets the first two lines, it knows nothing about the strText variable. If you have the Task List window open, you'll see a report of your error (If you can't see the Task List window, from the menu bars click View > Other Windows > Task List. Or hold down the Ctrl and the Alt keys on your keyboard, and the press the letter K.): The description of the error is "Local variable 'strText' cannot be referred to before it is declared". If you double click the icons on the left, VB.NET will highlight the error in your code. Move the "Dim … " Line back to the top, and not only do the blue wiggly lines go away, but the Task List will be erased. Design-time errors like the one above can be quite straightforward to correct. Others can be quite difficult, and you'll see the blue wiggly line but not understand how to correct the error. The Task List should be your first port of call when faced with such an error. his lesson is part of an ongoing tutorial. The first part is here: Design Time Errors Runtime errors are a lot harder than Design Time errors to track down. As their name suggests, these errors occur when the programme is running. Runtime errors are the ones that crash your programme. A simple way to crash a programme is to divided by zero. Change the code for your button to this, and try it out: Dim Num1 As Integer Dim Num2 As Integer Num1 = 10 Num2 = 0 TextBox1.Text = CInt(Num1 / Num2) The CInt( ) part means Convert to an Integer. We're just making sure to convert the answer to the sum into a number. But run your programme and test it out. Click your button and see what happens. What happens is that you'll get the following error message popping up: Click the Break button, and then stop your programme from running. When you try to divide by zero, VB.NET throws up the Overflow error message - there would be just too many zeros to go into the Integer variable type. Even if you change the Type into a Single or a Double, you'd still get the same error message. Programming environments just don't like you dividing a number by zero. If this were in a real programme, chances are it would crash, or "bug out". And you'll get the blame! If you think the answer to a calculation could result in zero, you should check for this. We'll see how to write code to trap Runtime errors in a moment. But here's another example of one. From the controls toolbox, add a RichTextBox control to your form. Change the Name property of your RichTextBox to rt1. A RichTextBox is just like a normal textbox but with more functionality. One of these extra functions is the ability to load a file directly. Delete or comment out any code you have for your button, and add the following line: rt1.LoadFile("C:\test10.txt", RichTextBoxStreamType.PlainText) All the line does is to load (or try to) the text file called "test10.txt" into the RichTextBox. The second argument just specifies that the type of file we want to load is a Plain Text file. Run your programme, and then click the button. If you don't have a text file called "test10.txt" in the root folder of your C drive, you'll get the following Runtime error message: The additional information is quite useful this time. It's saying that the file "C:\test10.txt" could not be found. If the error occurred in a normal programme, it would shut down. Not something you want a programme to do in mid stream! But let's see how to deal with it. This lesson is part of an ongoing tutorial. The previous part is here: Runtime Errors VB.NET has a inbuilt class that deals with errors. The Class is called Exception. When an exception error is found, an Exception object is created. The coding structure VB.NET uses to deal with such Exceptions is called the Try … Catch structure. In the coding area for your button, type the word Try. Then hit the return key on your keyboard. VB.NET completes the rest of the structure for you: Try Catch ex As Exception End Try The Try word means "Try to execute this code". The Catch word means "Catch any errors here". The ex is a variable, and the type of variable it is is an Exception object. Move your line of code from the previous section to the Try part: Try rt1.LoadFile("C:\test10.txt", RichTextBoxStreamType.PlainText) Catch ex As Exception End Try When you run your programme, VB will Try to execute any code in the Try part. If everything goes well, then it skips the Catch part. However, if an error occurs, VB.NET jumps straight to Catch. Add the following to your Catch part: MsgBox(ex.Message) Your coding window should look like this: Because ex is an object variable, it now has its own Properties and methods. One of these is the Message property. Run your programme and test it out. Click your button. You should see the following error message: The message is coming from the "additional Information" section of the error message we saw earlier, the one we didn't handle. But the point about this new message box is that it will not crash your programme. You have handled the Exception, and displayed an appropriate message for the user. If you know the kind of error that a programme might throw, you can get what Type it is from the Error message box you saw earlier. This one: Click the View Details links under Actions to see the following: The first line tells us the Type of Exception it is: System.IO.FileNotFoundException You can add this directly to the catch part. Previously, you were just catching any error that might be thrown: Catch ex As Exception But if you know a "file not found" error might be thrown, you can add that to the Catch line, instead of Exception: Catch ex As System.IO.FileNotFoundException You can keep the Exception line as well. (You can have as many Catch parts as you want.) This will Catch any other errors that may occur: Try rt1.LoadFile("C:\test10.txt", RichTextBoxStreamType.PlainText) Catch ex As System.IO.FileNotFoundException MsgBox(ex.Message) Catch ex As Exception MsgBox(ex.Message) End Try There is one last part of the Try … Catch Statement that VB.NET doesn't add for you - Finally: Try Catch ex As Exception Finally End Try The Finally part is always executed, whether an error occurs or not. You typically add a Finally part to perform any cleanup operations that are needed. For example, you may have opened a file before going into a Try … Catch Statement. If an error occurs, the file will still be open. Whether an error occurs or not, you still need to close the file. You can do that in the Finally part. But Microsoft advise that you always use Try … Catch Statements in your code. However, throughout the rest of this course, for convenience sake, we won't be using them much. Even when we should be.But that's no excuse for you not to use them! This lesson is part of an ongoing tutorial. The first part is here: Design Time Errors The third category of errors are the Logic errors. These can be thought of as coding errors. Your coding errors. They can be quite tricky to track down, and have you tearing your hair out with frustration. You will often hear yourself saying "But that should work! Why won't it!" Add another button to the form tou created in the first part, and try this code as an example of a logic error: Dim x As Integer Dim y As Integer Dim answer As Integer x = 10.5 y = 3 answer = x * y TextBox1.Text = answer When you've added the code to your button, run your programme and test it out. Before you click the button, what answer did you expect to get? You'd think that 10.5 multiplied by 3 would give you the answer 31.5. Click your button. The answer that appears in your textbox is 30! This is a logic error: when you don't get the answer you thought you'd get. The problem, if you were paying attention during the variable types sections, is that we are trying to put floating point numbers into an Integer variable type. The Integer variable only works with whole numbers. When you assign 10.5 to the variable x, the point 5 on the end gets chopped off. So only the 10 gets stored in x. 10 times 3 is thirty, and this is the answer that appears in the textbox. But the point is that VB.NET did not raise a Design-time error. Nor did it raise a Runtime error. The programme executed, and did not "bug out" on us. It just didn't give you the answer you expected - it was a logic error. Logic errors can be fairly simple to track down and solve. (The problem above can be solved by changing the variable types from Integer to Single or Double.) But they can also be quite difficult to track down. Especially as your code gets longer and longer. Here's another example of a logic error. Erase the code you have for button2, and add the following instead: Dim i As Integer Dim LetterCount As Integer Dim strText As String Dim letter As Char strText = "Debugging" For i = 1 To strText.Length - 1 letter = strText.Substring(1) If letter = "g" Then LetterCount = LetterCount + 1 End If Next TextBox1.Text = "G appears " & LetterCount & " times" All the code does is to try and count how many times the letter "g" appears in the word "Debugging". We're using a For loop, and Substring to get one letter at a time. This single letter is then placed inside the variable called letter. An If Statement is used to check if the letter is a "g". If it is, we increment the LetterCount variable. The answer we're expecting in the textbox is 3. Except, we don't get 3. We get zero: There were no wiggly lines and therefore no Build errors. When the button was clicked, a Runtime exception did not crash the programme. So that leaves a logic error. But where is it? In the next part, you'll learn how to use VB .NET's inbuilt tools to help you track down logic errors. This lesson is part of an ongoing tutorial. The first part is here: Design Time Errors In the last part, you added some code to a button. All the code does is try and count how many times the letter "g" appeared in the word "Debugging". We saw that the programme failed to do this, and came up with the answer zero. To help you find out what went wrong, there is a tool in VB .NET called a Breakpoint. Let's see what this is, and how to use Breakpoints. Breakpoints A breakpoint is like a note to VB.NET to stop your programme at a particular place. You add one to your code by clicking in the margins. A brown circled then appears, indicating where the code will break. The following two images show how to add one: When you click in the margins, to the left of a line of code, a brown circle appears: Notice that the line where you want VB.NET to break is highlighted brown. Run your programme, and click the button. You are immediately returned to the coding window. The place where you put the Breakpoint will now have a yellow arrow on top of the brown circle. The brown highlighted line will now be yellow: The yellow highlight indicates where in your code VB.NET is. To continue checking your code, press F10 on your keyboard (you can also press F11, but this will jump into any Subs or Functions you've set up.) The next line in your code will be highlighted: The yellow arrow, and the yellow highlight, jump down one line. Press the F10 key again. Then hold you mouse on the letter variable. The value this variable currently holds will be displayed: The first time round the loop, the value in letter is "e" (The "c" next to it means that the variable type is Character). If the "e" of "Debugging" is getting checked first, what happened to the "D"? Straight away, this indicates a problem. And the problem is that the Substring method starts counting from zero. So halt your programme by clicking "Debug > Stop Debugging", or click the Stop icon on the toolbar. Change the line in question to this: letter = strText.Substring(0) Run your programme again, and click the button. When you are returned to your code, press the F10 key and check the value of the letter variable. It should now be this: This time, the code is catching the first letter of the word when the loop begins, and not the second one. Is that it? Have we found the cause of our problems? Stop your programme. Click on the brown circle to get rid of the Breakpoint. Run it again, and see what happens. The number of G's counted is still zero! So the logic error has not yet been tracked down. Create another Breakpoint at the same place, and try again. You can continue pressing the F10 key until you've spotted the error. Or you can use another debugging tool - the Locals window. While your programme is still in Debug mode (the yellow line will still be there, if it is), click Debug > Windows > Locals from the menu bar. You should see the following in the bottom left of your screen: Locals means "Local variables". That is, variables declared in this section of the code. The variables i, letter and LetterCount are showing in the window. The value of these variables is also displayed: 0, Nothing and 0. Press F10 and these values will change. This is the Locals window after one go round the loop: The variable i is now 2; letter is "D", and LetterCount, is still 0. Keep pressing F10 and go round the loop a few times. What do you notice? You should notice that the value in letter never moves on. It is "D" all the time. And that's why LetterCount never gets beyond 0. Exercise Why does LetterCount never gets beyond 0? Correct the code so that your textbox displays the correct answer of 3 when the programme is run. And that's it for Error checking and debugging. It can often be an art form in itself. But one well worth persevering with: it could save you a lot of headaches! In the next section, we'll move on and have a look at what arrays are. n this section, you are going to learn all about the power of arrays, and how easy they can make your programming life. First, you need to know what an array is. What is an array? So far you've been using variables quite a lot. You've put numbers into variables, and you've put text into variables. But you've only done this one at a time: you've put one number into a variable, or one string of text. You've been doing this: Dim MyNumber As Integer MyNumber = 5 Or this Dim MyText As String MyText = "A String is really just text" Or even this: Dim MyNumber As Integer = 5 So one variable was holding one piece of information. An array is a variable that can hold more than one piece of information at a time. The MyNumber variable above held one number 5. If you had an array variable called MyNumbers - plural - you could hold more than one number at a time. You set them up like this: Dim MyNumbers(4) As Integer MyNumbers(0) = 1 MyNumbers(1) = 2 MyNumbers(2) = 3 MyNumbers(3) = 4 MyNumbers(4) = 5 When you set up an array with the Dim word, you put the name of your array variable, and tell Visual Basic how many items you want to store in the array. But you need to use parentheses around your figure. You then assign your data to a position in the array. In the example above we've set up an Integer array with 5 items in it. We've then said put number 1 into array position 0, put number 2 into array position 1, put number 3 into array position 2, and so on. You might be thinking that the array was set to the number 4 - MyNumbers(4) - but always remember that an array starts counting at zero, and the first position in your array will be zero. So that's what an array is - a variable that can hold more than one piece of data at a time -but how do they work? A programming example might help to clear things up. • Start a new VB project. • Add a Button to your Form. • Set the Text property of the Button to "Integer Array" • Put the following code behind your button: Dim MyNumbers(4) As Integer MyNumbers(0) = 1 MyNumbers(1) = 2 MyNumbers(2) = 3 MyNumbers(3) = 4 MyNumbers(4) = 5 MsgBox("First Number is: " & MyNumbers(0)) MsgBox("Second Number is: " & MyNumbers(1)) MsgBox("Third Number is: " & MyNumbers(2)) MsgBox("Fourth Number is: " & MyNumbers(3)) MsgBox("Fifth Number is: " & MyNumbers(4)) Test out the programme when you are finished. The numbers 10 to 50 should have been displayed in your message boxes. In the code, we first set up an Integer array with 5 items in it. Dim MyNumbers(4) As Integer We then assigned values to each position in the array. MyNumbers(0) = 1 To get at the values in the array, and display them in messages boxes, we just used the array name, followed by the position in the array. MsgBox("First Number is: " & MyNumbers(0)) So we've said, "Display whatever number is in array position 0, then display whatever number is in array position 1 ... " and so on. Add another messages box statement on a line below the others. Put this: MsgBox("Sixth Number is: " & MyNumbers(5)) Run your programme again, and click the Button. What happened? To explain what went wrong, and why, click the next part below. This lesson is part of an ongoing tutorial. This first part is here: What is an Array? In the previous part, you added some code to a button in order to test out arrays. When you clicked your button, you probably got an error box popping up, telling you that the "Index was outside the bounds of the array." This is the error message you may have received: The Index the error message is talking about is the figure in parentheses in your array. We set up this array Dim MyNumbers(4) As Integer And the highest Index number is therefore 4. But we tried to display something at index number 5: MyNumbers(5) Visual Basic said "Wait a minute, the idiot hasn't got a position number 5!" So it stopped the programme and gave you an error message. Delete this line from your code: MsgBox("Sixth Number is: " & MyNumbers(5)) So the way to get at information held in an array is through its Index number - "What's at array position 0? What's at array position 1?" A very handy way to get at the information in your array is by accessing its Index number in a For Loop. So that you don't have all those message boxes popping up, we can display the results in a List Box. Add a List Box to your form. Make it fairly wide, and just leave it on the default Name of ListBox1. Then change your code to the following (the new code is in Bold, red text): Dim MyNumbers(4) As Integer Dim i As Integer MyNumbers(0) = 10 MyNumbers(1) = 20 MyNumbers(2) = 30 MyNumbers(3) = 40 MyNumbers(4) = 50 For i = 0 To 4 ListBox1.Items.Add(MyNumbers(i)) Next i Run your programme, and click your button. Your form should look something like this one: The first time round the loop, the variable called i will hold the number 0. Visual Basic will test to see if our end condition is met. The end condition was "Loop until the variable i holds the number 4". The variable i only holds the number 0, so Visual Basic drops down to the next line: ListBox1.Items.Add(MyNumbers(i)) And what is inside the variable i? The number 0. So what's really getting adding to the List Box is this: MyNumbers(0) In other words, "Add to the List Box whatever is inside the array at position number 0" The next time round the loop, the variable i will hold the number 1. So this gets executed ListBox1.Items.Add(MyNumbers(1)) And the loop continues round and around, adding whatever is inside our array until the end condition for the loop is met. Change the first line of the For loop to this: For i = 0 To 5 Can you guess what will happen? Try it an see. Make sure you know why you get the error message before moving on. Arrays and Strings of Text Arrays can hold other types of data, too. They can hold Strings of text. • Put another Button on your Form • Set the Text property to "String Array" • Put the following code behind your Button Dim MyText(4) As String Dim i As Integer MyText(0) = "This" MyText(1) = "is" MyText(2) = "a" MyText(3) = "String" MyText(4) = "Array" For i = 0 To 4 ListBox1.Items.Add(MyText(i)) Next i When you have finished, run the programme and click your new button. The text you put into the 5 array positions should display in the List Box. Again, the same process is at work: Set up an array, and specify how many items you want to hold in the array; assign your data to each position; go round a loop and access whatever is in each position of the array. In the next part, we'll take a closer look at assigning values to an Array. his lesson is part of an ongoing tutorial. This first part is here: What is an Array? There are a number of way you can put data into each position of an array. The code we just wrote for the two buttons had known values stored into each position. We knew we that we wanted the numbers 1 to 5 to be stored into our Integer array, and we knew that we wanted the text "This is a String Array" stored into our String array. But you don't have to know what the values are. You can assign values straight from a Textbox into the position of your array. Like this: MyNumbers(0) = Val(Textbox1.Text) MyNumbers(1) = Val(Textbox2.Text) etc With that code, whatever you typed into the Textboxes on your Form would be stored into the positions of your array. The same would be true of a String Array: MyNumbers(0) = Textbox1.Text MyNumbers(1) = Textbox2.Text etc But do we have to keep typing out a value for each and every position of our array. What if we had an array with a hundred items in it, MyText(99)? Would we have to type out text for all one hundred positions of the array? Well, obviously not. You can use code to assign values to your array. Here is an example where we don't type out values for all positions of an array. It's the times table again. This time we'll use an array. And we'll write a line of code to assign values to each position of the array. • First, add another Button to your form. • Set the Text Property to "Times Table Array" • Add a Textbox to your Form • Set the Text Property to a blank string (in other words, delete Textbox1 from the Text property) • Add a Label near the Textbox • Set the Text property of the Label to "Which Times Table do you want?" • Now double click your new button to get at the code window. Add the following code: Dim numbers(10) As Integer Dim times As Integer Dim StoreAnswer As Integer Dim i As Integer ListBox1.Items.Clear() times = Val(TextBox1.Text) For i = 1 To 10 StoreAnswer = i * times numbers(i) = StoreAnswer ListBox1.Items.Add(times & " times " & i & " = " & numbers(i)) Next i Run the programme. Enter a number in your new text box, and then click the Times Table Array button. The times table for the number should have been printed. At the top of the code we set up three normal Integer variables, i, times and StoreAnswer. (We didn't really need the StoreAnswer variable, but it is here to make the code more readable.) We also set up an array. (Notice that we set it to 10. This actually gives us 11 positions in the array. But we're only putting something in positions 1 to 10. This is because it is more convenient for us, and for our Loop.) Dim numbers(10) As Integer We need to know what number we are going to be multiplying by, which times table we're working out. We get this number from the Textbox, and can assign it directly to the variable times times = Val(Textbox1.Text) We can then set up a For Loop. Inside the For Loop is where we'll assign values to each position of our array: numbers(i) = StoreAnswer First time around the loop, the variable i will hold a value of 1. So the second position of our array, numbers(1) will be assigned whatever is in the variable StoreAnswer The second time around the loop, the variable i will hold a value of 2. So the second position of our array, numbers(2), will again be assigned whatever is in the variable StoreAnswer We go round and round the loop assigning values to all ten positions of our array. The other two lines of code inside the array just work out the times tables, and Adds the answer to the List Box. Study them, and make sure you understand how they work. But the point of this is to demonstrate that you can use code to assign a value to a position in an array. In the next part, we'll take a look at situations where you don't know how many items will be in an array. This lesson is part of an ongoing tutorial. This first part is here: What is an Array? Study the following Form: In the above Form, the user is invited to enter values into three Textboxes. The first Textbox is for whatever times table he or she wants. The second Textbox asks for the starting value of the times table. The third Textbox is for the end number of the times table. In other words, 1 times 4, 2 times 4, 3 times 4, right up to 12 times 4. The point is that the user can enter any values he or she wants. We won't know until they are entered, and the button is clicked. Up until now, we've used an array with a fixed size. Our previous times table programme only went up to 10, and it started at 1. We used this to set up our array: Dim numbers(10) As Integer But that array would be no good for the above Form. Our array only held 11 positions. The user definitely wants the 4 times table right up to 12. Is there any way we can set up an array where the number of positions is not known? How can we set up a Non-Fixed size array? You do it like this. First set up an array with empty brackets Dim numbers( ) As Integer Next, pass the values from the Text Boxes to some variables times = Val(Textbox1.Text) startAt = Val(Textbox2.Text) endAt = Val(Textbox3.Text) We can then use these values to reset the array. You reset an array by using the ReDim word. You then specify the new values. Like this: ReDim numbers(endAt) Our original array did not have its size set - Dim numbers( ) As Integer. So we've got the end number from the Textbox. When we reset an array, we can use this new value. Since our user entered the value 12 for the end number, our array is now really this: Dim numbers(12) As Integer We can use the same variables for our For Loop. Then we can go round and round the loop assigning values to our array. To test this concept out, either start a new project, or amend the one you have displayed. Create three textboxes and labels. And add a new Button. Double click your button to open the code window. Then add the following code (the important line is in red): Dim numbers() As Integer Dim startAt As Integer Dim endAt As Integer Dim times As Integer Dim StoreAnswer As Integer Dim i As Integer times = Val(TextBox1.Text) startAt = Val(TextBox2.Text) endAt = Val(TextBox3.Text) ReDim numbers(endAt) For i = startAt To endAt StoreAnswer = i * times numbers(i) = StoreAnswer ListBox1.Items.Add(times & " times " & i & " = " & numbers(i)) Next i When you're finished, run your programme and test it out. Click the button and the times table should appear in the List Box. And that is how to set up an array when you don't know what size the array is going to be - set up an array with empty brackets. Reset the array with the ReDim word, and then give it some new values. Arrays can be a very tricky subject, and they dp take some getting used to. But they are well worth your time and effort - they'll make your coding life a lot easier! We'll move on to another subject - working with Strings of text. Humans are far from perfect. Especially when they are entering data into textboxes! Sometimes they won't enter any details at all in the boxes you want them to. And then when they do enter something, they often get it wrong. Sometimes on purpose, just to trip you up. By manipulating Strings of data, we can check things like text in a textbox to see if it is correct, and thereby gain some control of the user's actions. First, let's take a closer look at the String variable type. The String Variable Type There's more to the string variable type than meets the eye. You've used them a lot to store text. But the string variable types come with a lot of inbuilt power. Strings have their own properties and methods, just like a textbox or label or form does. That's because strings are objects. (In fact, all variables are objects in VB.NET, including the number variables.) In a later section, we'll be going into a bit more detail on objects. For now, think of them as things that can be manipulate - Like the textbox, label and form just mentioned. And strings variables can be directly manipulated, too. An example should clear things up. • Start a new project. • Add two textboxes and a button to your new form. • For Textbox1, set the Text property to “string variables”. • Double click the button to open the coding window. • Type the following as the code for the button: Dim strUpper As String strUpper = TextBox1.Text TextBox2.Text = strUpper.ToUpper( ) Run your code and see what happens when you click the button. You should have found that the text from Textbox1 gets converted to uppercase letters. The reason it gets converted is because we used the ToUpper method of the string variable. When you typed the full stop after the variable name, you probably saw this pop up box: Simply double click the method you want, and it's added to your code. strUpper.ToUpper( ) Notice that the name of the variable you want to do something with comes first. Then, after the full stop, you add the name of the method. It's easy to guess what some of the methods do (like ToLower), but others are a bit more enigmatic (Like Substring). In this section, we'll go through some of the string methods to see what they do, and how useful they can be in your code. Before we start, here's a full list of the methods that a string variable can access (it's a bit long, so it gets its own window!): Length and Chars on that list above are properties, and not methods. We'll be using these two, and they come in quite useful. Manipulating data from a Text Box You already know how to pass data from a Textbox into a variable. Just do this Dim FirstName As String FirstName = txtFirst.Text Then whatever was in the Textbox you called txtFirst will get transferred directly to the String variable you set up. Once the data is in the variable, you can test it to see if it's the type of data you want. After all, the user could have entered numbers to try and trip you up. Or they could have left it blank. • Add a new textbox to your form • Change the Name property to txtFirst • Add a second button to your form • Set the Text property to whatever you want • Double click the button and add the following code: Dim FirstName As String FirstName = txtFirst.Text If FirstName = "" Then MsgBox "Please enter your First Name in the text box" Exit Sub End If In this code, we are passing whatever is in the text box directly to the variable called FirstName. We are then testing what is inside the variable with an If statement. We want to test if the user has actually entered something into the text box. If they've left it blank, we want to tell them to try again. We also want to exit the Subroutine. After all, if they got it wrong, we don't want to proceed with any code we might have written. The way we are testing to see if the user has left the text box blank is this: If FirstName = "" Then We've put two sets of double quotes together. This signifies a string of text that is blank. If the user didn't enter anything at all, then our variable FirstName will contain a blank string. This is what we're testing for. Run the programme and try it out. Don't type anything at all in the textbox, but just click the button. The message box should display. Now, click inside the textbox. Hit the space bar three times. And then click the button. Did the Message box display? So why didn't it? After all, there was nothing in the textbox. Isn't that an blank string? What was passed to the variable? Well, when you press the space bar Visual Basic counts that as a text character. So when you press the space bar three times what is in the variable is this: FirstName = " " and not this: FirstName = "" The two are entirely different, according to Visual Basic. After all, you might have wanted three spaces! So how can we check to see if there is anything at all in our textbox? How do we defeat the user who has tried to fool us by hitting the space bar a number of times? In the rest if this section, you'll learn about the various ways you can use the String methods and properties to examine what a particular string contains. First up is the Trim method. In the previous part you added code to transfer some text that was in a Textbox over to a variable. The code you wrote was this: Dim FirstName As String FirstName = txtFirst.Text If FirstName = "" Then MsgBox "Please enter your First Name in the text box" Exit Sub End If But the user could press the spacebar in your textbox. Although there would be no letters or numbers inthe textbox, the above error checking wouldn't work - all of the blank spaces would get passed to your variable. We can use a String method called Trim to solve this problem. The Trim Method One of the methods on our list was Trim. What this does is to trim any leading or trailing blank spaces from a string. So if the string was " Text", then Trim would delete those spaces for you, leaving just "Text". You use it in your code. Like this: FirstName = txtFirst.Text FirstName = FirstName.Trim First, we put the text from the textbox into a variable called FirstName. Then we said "assign to the variable FirstName (FirstName = ) the value of FirstName trimmed (FirstName.Trim)". Again, though, we're just adding the method we want after the variable name. VB will take care of the trimming for us. Another way to Trim is to use the Trim() function directly. Like this: FirstName = Trim(txtFirst.Text) What you are trimming here is any blank spaces from around text entered directly in the text box called txtFirst But we now have a way to thwart that user who is trying to trip us up by entering blank spaces into our text box. If you were programming a Form where the First Name was going into a database, then it's essential you trap anything like this. OK, we've tested to see if the First Name text box was empty. Is there anything else we can do? What if our clever-clogs user tries to fool us again. This time he (they're always "he's"!) decides to enter some numbers. He claims his name is "George12345". Is there anything we can do to stop his little games? Is there a way to test that the data entered into a text box was text and not numbers? Indeed there is! We'll use the Chars Property to see if we can check for numbers and text. You'll also see the difference between Chars and Char. Char ( NOT Chars) Char is a variable type. It can hold one character at a time (the Char is short for Character). You set it up like this: Dim OneCharacter As Char You can then store a character in the variable like this: OneCharacter = "A" Or like this: Dim OneCharacter As Char = "a" You can even do this: Dim OneCharacter As Char = "apple" But if you try to put a whole word into a Char variable, only the first letter will be retained. So what good is the Char variable type? Well, a common use for it is to transfer one letter at a time from a string, and then test to see what this character is. You can test to see if it's a number, for example. Or perhaps to test if the string contains an "@" symbol for a valid email address. We'll test for a number. In the process, we can study the Length property of string variables. Add another textbox and a button to your form from the first part of the tutorial. Change the Name property of the textbox to txtChars. For the Text property of the Textbox, enter "George123". Double click the new button and enter the following variable declarations: Dim OneCharacter As Char Dim FirstName As String Dim i As Integer Dim TextLength As Integer Remember what we're going to be doing here. We're going to put the text from the textbox into a string variable. Then we'll loop round every character in the string to see if it's a number. So the next line to add to your code is the one that transfers the text from the textbox to the string variable. Add this: FirstName = Trim(txtChars.Text) The next thing we need is the length of the string. We need this for the end value of our loop. The length property will give us this answer. So add this line: TextLength = FirstName.Length The length property of a string variable tells you how many characters are in the string. You can add a message box to test out your code so far: MsgBox("Number of characters is: " & TextLength) Run your programme. Click the button and test out your code. You should see a message box popping up like this one: So we've found out that "George123" has 9 characters. We can now loop round each character in the string and test which ones are the numbers. Add the following For loop to your code (you can delete or comment out your message box line now): For i = 0 To TextLength - 1 Next i So the For loop starts at zero and ends at the length of the text, minus 1. (It will loop from 0 to 8 in our code - 9 characters. We'll see why you have to deduct 1 soon. Inside of our loop, we need to grab one character at a time, and then put it into our Char variable. You can do that with the Chars() Property of the string variable type. Chars (NOT Char) Chars is a method of the String variable type. You can use it on any length of string, not just a Char variable. And that's the difference between the two: Char is a variable type, while Chars is a method you can use on Strings. Chars works like this: OneCharacter = FirstName.Chars(i) You type the name of your variable, then after the full stop you add Chars(). Inside of the round brackets, you need a number. This number is the position in the string you want to grab. So if you wanted the third letter of a string variable, you'd put this: Dim SomeString As String Dim OneCharacter As Char SomeString = "George123" OneCharacter = SomeString.Chars(2) The variable OneCharacter would then hold the third letter - "o". The reason we've put 2 inside of the round brackets and not 3 is because VB starts counting the characters from zero, and NOT 1. And that's why our For Loop is this: For i = 0 To TextLength - 1 You have to deduct 1 because the Chars() count starts at zero. So amend your For Loop to this: For i = 0 To TextLength - 1 OneCharacter = FirstName.Chars(i) MsgBox(OneCharacter) Next i Run your code, and then click your button. You should get a message box displaying. In fact, you'll get 9 message boxes, one for each character in the string! Ok, try these exercises to test your new knowledge. Exercise Add an If statement to your For Loop. Check each character of the string "George123". If you find a number, display a suitable message, something like "A number was found". Exit the for loop when the first number is found. To check if a variable is a number, you can use the IsNumeric( ) function. This function will return either True or False. In other words, if the variable being checked is a number, then IsNumeric( ) is True; if IsNumeric( ) is not a number then False gets returned. If IsNumeric(OneCharacter) Then Exercise Amend your code to keep a count of how many characters in the string are numbers. Display the count in a message box. In the next part, we'll take a look at another useful String method - InStr. String Position The InStr( ) method of string variables tells you what the position of one string is inside another. For example, if your string was "me@me.com" and you wanted to know if the string contained the @ symbol, you could use InStr( ) Method. You would use it like this FirstString = "me@me.com" SecondString = "@" position = InStr(FirstString, SecondString) The variable FirstString is the string we want to search; SecondString is what we want to search for. You can specify a starting position for the search to begin. If you do, this number goes at the start (the default is zero): position = InStr(1, FirstString, SecondString) The variable called position has to be an integer variable. That's because the InStr() Method returns a number, and not text. In the code above, position would have a value of 3. That's because the @ symbols starts at the third letter of "me@me.com". (Note: the InStr() Method starts counting at 1, and not zero like Chars(), which is very confusing!) If the string you're searching for is not found, then the value placed inside of your integer variable (position in our case) is zero. That enables you to code something like this: If position = 0 Then MsgBox "Not a Valid email address: There was No @ Sign" End If Another useful string method is Substring. We'll see how to use it in the next part. Substring Another useful string method is Substring. This allows you to grab one string within another. (For example, if you wanted to grab the ".com" from the email address "me@me.com") In between the round brackets of Substring( ), you specify a starting position, and then how many characters you want to grab (the count starts at zero again). Like this: Dim Email as String Dim DotCom as String Email = "me@me.com" DotCom = Email.Substring(5, 4) MsgBox(DotCom) The message box would then display the characters grabbed from the string, in this case the ".com" at the end (start at position 5 in the string and grab 4 characters). You could also do a check to see if an email address ended in ".com" like this: Dim Email As String Dim DotCom As String Email = "me@me.con" DotCom = Email.Substring(Email.Length - 4, 4) If DotCom = ".com" Then MsgBox("Ends in Dot Com") Else MsgBox("Doesn't End in Dot Com") End If The starting position for Substring( ) this time is "Email.Length - 4". This is the length of the string variable called Email, minus 4 characters. The other 4 means "grab four characters" You have to be careful, though. If there wasn't four characters to grab, VB would give you an error message. We could replace the Chars() For loop code we wrote earlier with a Substring() method. The result would be the same. Here's the code: For i = 0 To TextLength - 1 OneCharacter = FirstName.Substring(i, 1) MsgBox OneCharacter Next i So we're saying, "Start grabbing characters from the position i. Just grab one character". Substring and Chars are very useful methods to use when you want to check the letters in a string of text. In the next part, we'll take a look at the Equals, Replace, and Insert Methods. The Equals Method In code previously, we had this: If DotCom = ".com" Then MsgBox("Ends in Dot Com") Else MsgBox("Doesn't End in Dot Com") End If You can use the Equals method of string variables in the first line, instead of an equals ( = ) sign: If DotCom.Equals(".com") Then So after the name of your string variable comes the full stop. Then select "Equals" from the popup list. In between the round brackets, you type the string (or variable name) that you want VB to compare. The Equals method is used to compare one string of text against another. If they're the same a value of True is returned, else it's False. The Replace Method You can replace text in one string with some other text. The process is fairly straightforward. Here's some code that uses replace. Add a button to a form and test it out: Dim OldText As String Dim NewText As String OldText = "This is some test" NewText = OldText.Replace("test", "text") MsgBox(OldText) MsgBox(NewText) When you run the programme, the first message box will say "This is some test" and the second box will say "This is some text". The text you want to get rid of comes first. Then after a comma, type the new text. You can use string variables rather than direct text surrounded by double quotes, for example: Dim NewWord As String = "Text" NewText = OldText.Replace("test", NewWord) The Insert Method You can also insert some new text into an string. Here's some code to try out: Dim SomeText As String Dim NewText As String SomeText = "This some text" NewText = SomeText.Insert(5, "is ") MsgBox(SomeText) MsgBox(NewText) The 5 in round brackets means start at position 5 in the string variable SomeText (the count starts at zero). You then type the text that you want inserted. You can use a variable name instead of direct text surrounded by quotes. In the next part, we'll take a look at how to use Split() and Join in VB .NET. Two very useful string variable methods are Split and Join. Split() allows you to split a line of text and put each element (word or phrase) into an array; Join() allows you to join elements of an array into one line of text. An example or two might clear this up. The Split() Method In a later project, you'll have to open up text file and read it's contents. You can read the text file line by line, and each line might be something like this: "UserName1, Password1, UserName2, Password2, UserName3, Password3" The programming problem is to separate each word. You can use Split for this. Each word would then be separated, ready for you to place into an array. Here's an example for you to try out. (It's better to put this code behind a new button): Dim LineOfText As String Dim i As Integer Dim aryTextFile() As String LineOfText = "UserName1, Password1, UserName2, Password2" aryTextFile = LineOfText.Split(",") For i = 0 To UBound(aryTextFile) MsgBox(aryTextFile(i)) Next i Notice the line that sets up an array: Dim aryTextFile() As String We don't know how many elements will be in the array (how many words on each line), so we leave the round brackets blank. The next line just put some text into a variable called LineOfText. But this can come from a text file that you open with code. The line that does the splitting comes next: aryTextFile = LineOfText.Split(",") Notice that aryTextFile has now lost its round brackets. If you put them in, you get an error. The use of the Split() method, though, is this: LineOfText.Split(",") After the name of your variable and the full stop, select (or type) the word Split. In between round brackets you put what is know as the separator. This is the symbol or punctuation mark that you are using to separate each element of your line. In our case, we're using a comma to separate the words in the line. But you can use anything you like (a hyphen, for example). When VB finishes the splitting, it fills up your array. Each element will occupy one slot in your array. So in our example, aryTextFile(0) will hold a value of UserName1, aryTextFile(1) will hold a value of Password1, etc. The For loop is there to show you how to loop round each element in your array, and displays the results in a message box: For i = 0 To UBound(aryTextFile) MsgBox(aryTextFile(i)) Next i The first line includes this: UBound(aryTextFile) UBound means Upper Boundary of an array. In between the round brackets of UBound() you type the name of your array. Notice, though that the round brackets of the array have gone missing again. So if your array was this: MyArray(9) The Upper Boundary of the array would be 9. So the end of the For Loop would then be 9. You code like this when you don't know how many elements are in your array. The message box just displays what is in each position of your array: MsgBox(aryTextFile(i)) The point is that all of the words from your line of text have been split and placed into an array. You now need to know how to put the text back together again. The Join() Method The Join method is used when you want to join the elements of an array back together again. Here's some code which does exactly that. Dim LineOfText As String Dim i As Integer Dim aryTextFile(3) As String aryTextFile(0) = "UserName1" aryTextFile(1) = "Password1" aryTextFile(2) = "UserName2" aryTextFile(3) = "Password2" LineOfText = String.Join("-", aryTextFile) MsgBox(LineOfText) The line that joins each element in the array is this: LineOfText = String.Join("-", aryTextFile) (NOTE: If you have an older version of the VB NET software, use LineOfText.Join instead of String.Join.) In between the round brackets of Join(), you first type what you want to use as a separator. Here, we're using an hyphen as a separator. Next, you put the name of your array. Again the round brackets from the array have gone missing. When the line executes, the variable LineOfText will hold the following: "UserName1-Password1-UserName2-Password2" Once you have the array elements joined together, you could then write the line back to your text file. Split and Join can be very useful indeed. Especially when you're working with text files. Speaking of which, the next section deals with exactly this subject. There is a very useful object in VB.NET called System.IO (the IO stands for Input and Output). You can use this object to read and write to text files. We're going to be having a closer look at objects (and what System is) in the next section. For now, let's just see how to open up a text file using the System.IO object. First, here's an explanation of just what we mean by "text file". What is a Text File? The files on your computer all end in a three letter extensions. Microsoft Word files will have a different three letter extension from Microsoft Excel files. The extension is used to identify one file type from another. That way, Excel won't try to open Word files, or vice versa. You can just write some code to strip the last three letters from the file name, and then check that these three letters are the ones you want. Rather like the code you wrote to strip the last three letters from an email address. Text files have an extension that ends in .txt. The Windows operating system gives you a good, basic Text Editor in Notepad. The Notepad programme allows you to save files with the .txt extension. In other words, as Text Files. These Text Files can then be opened by a wide variety of programmes. A simple text file like this is called a Sequential File, and that is what we will be opening here. So let's begin. The ability to open up a text file and read its contents can be very useful to you in your programming life. You might have a text file containing quiz questions and answers, for example. You could read the questions and answers from a text file and create your own "Who wants to be a Millionaire" game. Or you might want to save some data associated with your programme, and then open it up again when the programme starts. Well see how to open up a text file in VB .NET right now. In a later section, you'll learn how to save data to a text file. To open up a text file, you need to create something called a "StreamReader". This, as its name suggests, reads streams of text. The StreamReader is an object available to System.IO. You create a StreamReader like this: Dim FILE_NAME As String = "C:\test.txt" Dim objReader As New System.IO.StreamReader(FILE_NAME) The first line just sets up a string variable called FILE_NAME. We store the path and name of our text file inside of the string variable: = "C:\test.txt" We're saying that there is a text file called test which is at the location (path) "C:\". You set up the StreamReader to be a variable, just like a String or Integer variable. But we're setting up this variable differently: Dim objReader As New System.IO.StreamReader(FILE_NAME) We've called the variable objReader. Then, after the "As" word comes "New". This means "Create a New Object". The type of object we want to create is a StreamReader object: System.IO.StreamReader Sysytem is the main object. IO is an object within System. And StreamReader is an object within IO. StreamReader needs the name of a file to Read. This goes between a pair of round brackets: System.IO.StreamReader(FILE_NAME) VB will then assign all of this to the variable called objReader. So instead of assigning say 10 to an Integer variable, you are assigning a StreamReader to a variable. Read To End But this won't do you any good. We haven't actually opened the text file yet. We've just told VB where the text file is and what object to open it with. You do the opening like this: TextBox1.Text = objReader.ReadToEnd Now that objReader is an object variable, it has its own properties and methods available for use (in the same way that the textbox has a Text property). One of the Methods available to our new StreamReader variable is the ReadToEnd method. This will read the whole of your text, right to the end. We're then popping this in a textbox. Let's test all this theory out. Do the following: • Start a new project • Add a textbox to your new form, and just leave it on the default Name of Textbox1 • Set its MultiLine property to True • Add a Button to your form • Double click the button and add the following code for it: Dim FILE_NAME As String = "C:\test.txt" Dim objReader As New System.IO.StreamReader(FILE_NAME) TextBox1.Text = objReader.ReadToEnd objReader.Close() The last line closes the StreamReader we set up. You have to close your stream objects after you’ve used them, otherwise you’ll get errors messages. When you’re done, run your programme and click your Button. Unless you already have a file called test.txt at the location C:\ you’ll get this error message popping up: The last line spells it out clearly: Could not find file "C:\test.txt". So we were trying to read a text file that doesn't exist. Does the File Exist? You can, though, test to see if the file exists. If it does, you can open it; if not, you can display an error message. Amend your code to this (the new lines are in bold, red): Dim FILE_NAME As String = "C:\test.txt" If System.IO.File.Exists(FILE_NAME) = True Then Dim objReader As New System.IO.StreamReader(FILE_NAME) TextBox1.Text = objReader.ReadToEnd objReader.Close() Else MsgBox("File Does Not Exist") End If We've now wrapped up our code in an If Statement. The first line of the If Statement is this: If System.IO.File.Exists(FILE_NAME) = True Then This tests to see whether or not a file exists. Again, you start with System.IO. Then you access another object of System.IO - the File object. This has a method called Exists. In between the round brackets, you type the name (or variable) of the file you want to check. The value returned will either be True (if it does exists), or False (if it doesn't). If the file exist then we can go ahead and create our StreamReader; If it doesn't, we can display a error message for the user. So that your programme will work, there is a file below called "test.txt". Download this to your computer, in the main C:\ folder (Right click the file and select Save Target As (IE), or Save Links As (Firefox): When you have done that, run your programme again. Click the button once more, and you should see the text from your file appear in the textbox. (If you get the error message again, it means you haven't copied the file to the right place.) In the next part, we'll see how to read the contents line by line, instead of all in one go. Quite often, you don't want to read the whole file at once. You want to read it line by line. In which case, instead of using the ReadToEnd method, as we did in the previous section, you can use the ReadLine method: The ReadLine method, as its name suggests, reads text one line at a time. In order to do this, though, you need to use a loop. You can then loop round each line and read it into a variable. Here's a coding example: Dim TextLine As String Do While objReader.Peek() <> -1 TextLine = TextLine & objReader.ReadLine() & vbNewLine Loop The first line of the Do While loop is rather curious: Do While objReader.Peek() <> -1 The Peek method takes a peek at the incoming text characters. It's looking ahead one character at a time. If it doesn't see any more characters, it will return a value of minus 1. This will signify the end of the text file. Our loop checks for this minus 1, and bails out when Peek has this value. Inside the loop, we're reading each line from the text file and putting into new variable. (We're also adding a new line character on the end. Delete the & vbNewLine and see what happens). objReader.ReadLine() So the ReadLine method reads each line for you, instead of the ReadToEnd method which gets the whole of the text file. Once you have a line of text in your variable, though, it's up to you to parse it. For example, suppose the line of text coming in from the text file was this: "UserName1, Password1, UserName2, Password2" You would then have to chop the line down and do something which each segment. VB won't do this for you! (But you saw how to do this in the last section, when you used things like Split and Substring.) But what you are doing in the Do Loop is building up your variable with lines of text that are pulled from your text file. Once you have pulled all the text from your file, you can then put it into the text box. Here's our programme once more, with the new code highlighted in bold, red text: Dim FILE_NAME As String = "C:\test.txt" Dim TextLine As String If System.IO.File.Exists(FILE_NAME) = True Then Dim objReader As New System.IO.StreamReader(FILE_NAME) Do While objReader.Peek() <> -1 TextLine = TextLine & objReader.ReadLine() & vbNewLine Loop Textbox1.Text = TextLine Else MsgBox("File Does Not Exist") End If So inside the loop, we go round building up the TextLine variable. Once all the file has been read (when Peek() has a value of -1), we then place it into Textbox1. In the next part, you'll learn how to write to a text file. Writing to a text file is similar to reading a text file. Again we use System.IO. This time, instead of using the StreamReader we use the StreamWriter. The StreamWriter is used to write a stream of text to a file. Add another Button to the form you've been working on. Set the Text property of the button to "Write to File". Double click your new button to open up the coding window. Add the following: Dim FILE_NAME As String = "C:\test2.txt" If System.IO.File.Exists(FILE_NAME) = True Then Dim objWriter As New System.IO.StreamWriter(FILE_NAME) objWriter.Write(TextBox1.Text) objWriter.Close() MsgBox("Text written to file") Else MsgBox("File Does Not Exist") End If Run your programme, and then click your new button. Unless you have a file called "test2.txt", you should see the message box display: "File Does Not Exist." Once again, VB insists that the file must exist before it can actually do something with it. Which is not unreasonable! Stop your programme and change this line: Dim FILE_NAME As String = "C:\test2.txt" To this: Dim FILE_NAME As String = "C:\test.txt" In other words, just change the file name back to test.txt. (Hopefully, you haven't deleted the test.txt file from your hard drive!) Run your programme again. Type something into the textbox, and then click your button. You should see the message box "Text written to file" appear. But notice that if you open up the text file itself, any text you had previously will be gone - it has been overwritten, rather than appended to. (We'll see how to append text to a file shortly.) Let's have a look at the code we wrote, though. Once again, we check to see if the File Exists. If it's True that the file exists, then the first line that gets executed is setting up our variable: Dim objWriter As New System.IO.StreamWriter(FILE_NAME) It's almost the same as last time. Only two things have changed: we created a new variable name, objWriter, and we're now using StreamWriter instead of StreamReader. Everything else is the same. To write the text to our file, we've used this: objWriter.Write(TextBox1.Text) After the name of our variable (objWriter), we typed a full stop. The drop down box appeared showing available properties and methods. The "Write" method was chosen from the list. In between round brackets, you put what it is you want VB to write to your text file. In our case, this was the text in Textbox1. You can also do this: objWriter.Write("Your Text Here") The above uses direct text surrounded by double quotes. This is also acceptable: Dim TheText As String = "Your Text Here" objWriter.Write(TheText) This time, we've put the text inside of a variable. The name of the variable is then typed inside of the round brackets of "Write". But you don't have to write the whole text at once. You can write line by line. In which case, select WriteLine from the available properties and methods. Here's an example of how to use WriteLine: Dim FILE_NAME As String = "C:\test.txt" Dim i As Integer Dim aryText(4) As String aryText(0) = "Mary WriteLine" aryText(1) = "Had" aryText(2) = "A" aryText(3) = "Little" aryText(4) = "One" Dim objWriter As New System.IO.StreamWriter(FILE_NAME) For i = 0 To 4 objWriter.WriteLine(aryText(i)) Next objWriter.Close() The error checking code has been left out here. But notice the new way to write text to the file: objWriter.WriteLine(aryText(i)) We're looping round and writing the contents of an array. Each line of text from the array gets written to our text file. But each line is appended. That is, the text file doesn't get erased after each line has been written. All the lines from the array will be written to the text file. However, if you were to run the code a second time then the contents of the file are erased before the new WriteLine() springs into action. In other words, you'd only get one version of "Mary WriteLine had a little one" instead of two. In the next part we'll see how to add text to a file that already contains text - called appending to a file. There will be times when you won't want to erase all the text from your file. You'll only want to add text to what you currently have. In which case you need to Append. Appending text to your file is quite easy. When you set up the object variable for the StreamWriter, which you did here, you just typed the name and path of the file: Dim objWriter As New System.IO.StreamWriter(FILE_NAME) To append text to a file, you type a comma after your file name then type the word True: Dim objWriter As New System.IO.StreamWriter(FILE_NAME, True) If you want to add some text to the file, you need that True value. If you leave out the True or False, a new file is not created. Here some code that appends text to the file we wrote to: Dim FILE_NAME As String = "C:\test.txt" Dim i As Integer Dim aryText(4) As String aryText(0) = "Mary WriteLine" aryText(1) = "Had" aryText(2) = "Another" aryText(3) = "Little" aryText(4) = "One" Dim objWriter As New System.IO.StreamWriter(FILE_NAME, True) For i = 0 To 4 objWriter.WriteLine(aryText(i)) Next objWriter.Close() MsgBox("Text Appended to the File") The lines that have changed are in bold, red. But as you can see, not much has changed! But try both version and see how they work. Creating a file if it doesn't exist If you want to create a file if one doesn't exist, the process is again quite simple: Dim objWriter As New System.IO.StreamWriter(FILE_NAME, False) This time, we've just added the word "False" to the end of FILE_NAME. This will ensure that a new text file is created if one doesn't exist. In the next part, we'll see how to copy a file in VB .NET. You can also copy a file that you've created. This time, we don't need the StreamWriter or StreamReader of System.IO. We need the File object: System.IO.File This just means "System.IO has an object called File. Use this File object". File has it's own properties and methods you can use. One of these is Copy. Here's some code that makes a copy of our test file . Dim FileToCopy As String Dim NewCopy As String FileToCopy = "C:\test.txt" NewCopy = "C:\NewTest.txt" If System.IO.File.Exists(FileToCopy) = True Then System.IO.File.Copy(FileToCopy, NewCopy) MsgBox("File Copied") End If The file we want to copy is called "C:\test.txt". We've put this inside of a string variable called FileToCopy. The name of the new file we want to create, and its location, are assigned to a variable called NewCopy. Next, we have to check to see if the file we're trying to copy exists. Only if it does should we go ahead and copy it. You've met this code before. Inside of the If Statement, we have this: System.IO.File.Copy(FileToCopy, NewCopy) We use the Copy method of System.IO.File. In between the round brackets, you first type the name of the file you want to copy. After a comma, you then type the name of the new file and its new location. In the next part, we'll see how to Move a file. You move a file in a similar manner as you did to Copying a File - specify a source file and a new destination for it. This time, we use the Move method of System.IO.File. Here's some code: FileToMove = "C:\test.txt" MoveLocation = "C:\ TestFolder\test.txt" If System.IO.File.Exists(FileToMove) = True Then System.IO.File.Move(FileToMove, MoveLocation) MsgBox("File Moved") End If The above code assumes that you have created a folder on your hard drive called "TestFolder": MoveLocation = "C:\ TestFolder\test.txt" The file called test.txt will then be moved inside of this new location. You can give it a new name, if you want. In which case, just change the name of the file when you're moving it: MoveLocation = "C:\ TestFolder\NewName.txt" Again though, the thing to type in the round brackets of the method is first the Source file, then the Destination. System.IO.File.Move(FileToMove, MoveLocation) In the final part of this section, you'll learn how to Delete a File using VB .NET code. Deleting a file is quite simple - but dangerous! So be very careful when you're trying out this code. Make sure the file you're going to delete is not needed - you won't be able to restore it from the recycle bin! To delete a file from your computer, you use the Delete method of System.IO. Here's some new code for you to try: Dim FileToDelete As String FileToDelete = "C:\testDelete.txt" If System.IO.File.Exists(FileToDelete) = True Then System.IO.File.Delete(FileToDelete) MsgBox("File Deleted") End If First, we've set up a string variable called FileToDelete. We've then assigned the name of a file to this variable - "C:\testDelete.txt". (We created this file first, and made sure that it was safe to junk it!) Next, we test to see if the File Exists. In the IF Statement, we then had this: System.IO.File.Delete(FileToDelete) After selecting the Delete method, you type the name of the file you want to get rid of. This goes between a pair of round brackets. And that's it! That's all you need to do to delete a file from your computer, never to see it again. So be very careful when you test out the code! OK, enough of Text Files. In the next section, we'll look at Functions and Subs. So far, the code you have been writing in these tutorials has mostly been lumped together under one button. The problem with this approach is that your code can get quite long and complex, making it difficult to read, and difficult to put right if something goes wrong. Another approach is to separate some of this code into its own routine. This is where functions and subs come in. Segements of Code to do a Particular Job The two terms refer to segments of code that are separate from your main code. You've already met some string functions - Equals() and Substring(), for example. These functions are built into Visual Basic. But if you could see under the hood, what you'd find is some code to do these jobs for you. All you have to do is to specify, for the Substring() function, what the string is, where you want to start, and how many characters you want to grab. You don't have to worry about how Visual Basic gets your answer, because the code is all wrapped up in a function, ready for you to use over and over again. And that's the point about Functions and Subs: it's code that you might want to use over and over again. You don't have to keep writing the same code every time you want a specific job doing. Just write the code once, and then when you want to use it, just let Visual Basic know. Write a Function or Sub to do the Job Think about error checking when people are entering data on your Forms. You'd probably have a lot of Text Boxes, and want to check that the user was entering the correct data. You don't want people entering numbers in your First Name text box, for instance. To check that the user has entered the correct data, you write some error checking code. Except you might have lots of text boxes on the form. If you want to check all the text boxes, you'd have to write the same "checking" code for each text box. Instead of doing that, you can write your own Function or Sub. You only have to write it once. Then when you want to use it, you just refer to it by name, and the code will get executed. We'll soon write a Sub that we can use over and over again. The difference between Functions and Subs First, though, in case you are wondering what the difference is between a Function and a Sub, it's this: Functions return a value, and Subs don't. Substring() is a Function, because you want some sort of answer back, and an answer that you can then use elsewhere. You assign the answer to the Substring() function to a variable. A Sub is some code or job that you want VB to get on with and execute. An example is closing a form down and unloading it with Me.Close(). You don't need to return a value, here; you just want VB to close your form down. An example or two might help to clear things up. We'll start that on the next page. In the previous part, you learnt what a Sub is, and that it doesn't return a value, unlike a Function. In this part, you'll learn how to create your own Subs in VB .NET. Sub, by the way, is short for Subroutine Here’s what we’re going to do. We’ll set up a text box on a form. The text box will be a First Name text box, and we’ll be checking that the user has actually entered something into it. So, do this: • Start a new project, and • Put a Text Box on your new Form. • Put a button on the Form, too. • Double lick your button to see the coding window • Add the following code for the button: Dim TextBoxData As String TextBoxData = Trim(TextBox1.Text) If TextBoxData = "" Then MsgBox("Please Enter your First Name") End If Run the programme and test it out. Don’t enter anything in your textbox, but just click your button. Your message box should display. Now, all that code is inside the button. More likely than not, we'd be writing more code for that button. In fact, we could be writing lots of code. The code we write could get a bit long and complex. Do we have to have that error checking code in there? And wouldn't we have to type it out all over again, if we wanted to check another textbox from a different button? The answer to our two questions are, Not at all, and Yes we would! To solve the problem, we'll chop that code from the button, and write a Sub for it. To write your own Sub, your cursor needs to be outside of the button code, and on a new line. But before the "End Class". So, on a new line outside the button code type the following: Private Sub ErrorCheck() When you've typed that, hit the enter key on your keyboard. Visual Basic will add the End Sub for you. The name "ErrorCheck" is entirely our own, and we could have called it almost anything we liked. But it's better to stick to something descriptive. Your code window will then look like this one: Now, cut the code from your button and paste it between these two new lines, where the cursor is in the image above. You have just created your own Subroutine! How to use your new Sub But the Sub is not doing much good where it is. We need a way to use that code. To use our new Sub, we have to tell Visual Basic to execute the code. We do that simply by referring to the Sub by name. So click inside the button code, just before the End Sub of the button. Type the following: Call ErrorCheck() You don't have to use the "Call" word. Try taking that word out altogether, and then testing the programme again. The programme should run exactly the same. But using the "Call" word makes your code easier to read, and tells you that you are executing your own Subroutine on this line. Your coding window should now look like this: Run your programme and test it out. You should get the Message Box again, when nothing is in the Textbox. Add another button to your form. Double click the new button to get at the code. Then type Call ErrorCheck() as the code for it. Run your programme again, and click your new button. You should get the Message box popping up, when nothing is entered into the Textbox. The point about this is that you have created your own code segment. You can use this segment of code whenever you like, just by referring to it by name. Of course, you can have your code check more than one Textbox. You can check as many as you like. And for whatever you like. You can include the code you wrote to check for a correct email address, as well. But all that error checking code is no longer clogging up your button code. In the next part, we'll take a look at how you can pass text from a text box to your Subroutines - Paramaters, in other words. In this lessons, we're going to be exploring Parameters. let's get straight to it. Add two more textboxes to the form you created in the previous part. then do the following: • Set the Name property of the first Textbox to txtFirstNumber • Set the Name property of the second Textbox to txtSecondNumber • Add a new button to your Form and set the Text property to "Get Answer" The two textboxes will contain numbers, one for each box. We'll write code to add the two numbers together, but in our own Sub. When the button is clicked, a Message Box will pop up revealing the answer to the sum of the numbers in the textboxes. Double click your new button to bring up the code window. Click outside of the button code, just after End Sub, but before End Class. Type the following code: Private Sub AddNumbers() Dim first As Integer Dim second As Integer Dim answer As Integer first = Val(txtFirstNumber.Text) second = Val(txtSecondNumber.Text) answer = first + second MsgBox("The total is " & answer) End Sub We have created a Sub to add together the two numbers from the Textboxes. The code is very simple, and you should be able to follow it without any problems. Now add this line to the code for your "Get Answer" button: Call AddNumbers() Run your programme. Type a number in each of the two Textboxes, and click your button to make sure your programme works (did the Message Box display?) Stop the programme and return to the design environment. Chop the two lines of code for the Textboxes from the Sub and put them into the button. Your two sections of code should now look like this: The reason why there are two wiggly lines under first and Second is that the AddNumbers Sub knows nothing about these two variables. We've only declared one variable inside the Subroutine - answer. To get rid of the wiggly lines, we can set up something called a Parameter. Well, two parameters. To put it simply, a Parameter is a value that we want to pass from one code section to another. What we want to do is to pass the values we gathered from our button code and hand them over to our AddNumbers Sub. So how do we do that? Change the Private Sub AddNumbers() line to this: Private Sub AddNumbers(first As Integer, second As Integer) When you press your return key, VB changes the part in round brackets to this: (ByVal first As Integer, ByVal second As Integer) It's added a curious term - ByVal. We'll explain what that is in a moment. For now, concentrate on the Parameters. The parameters are what we want to hand to our Subroutine. We want to hand an integer variable called first, and an integer variable called second. Whatever values are currently stored in these two variables will be handed to our Sub. But we need to change our Calling line, the one from our button. This line now has a wiggly line under it, signifying that something is wrong. Remember, it was this: Call AddNumbers() If you hold your mouse over the AddNumbers() you might see this tip appear: What this is telling you is that your AddNumbers Sub takes some Parameters (They are called Arguments when you pass them, and Parameters when they are received. Because this is somewhat confusing, we'll stick to calling them Parameters.) In other words, you don't have any option: if you want to call this Sub, you have to add values for the parameters you set up. So change you Calling line to this: Call AddNumbers(first, second) (If the second inside your Sub has changed to Second(). Delete the round brackets.) Again, we use the parentheses. And in between the parentheses are our two variables. They don't have to have the same names. Whatever you call your variables in the AddNumbers Sub does not have to be the same names as the calling line. The variable names can be entirely different. But the values in the variables get passed in the order you set them up. In our case the value in the variable first will get passed to the first variable in our AddNumbers Sub; the value in the variable second will get passed to the next variable we set up in our AddNumbers Sub. Run your programme and check that it is working properly, now that you have changed the calling line. When you are done, change the variable names for your AddNumbers Sub to this: Private Sub AddNumbers(ByVal first2 As Integer, ByVal second2 As Integer) Dim answer As Integer answer = first2 + second2 MsgBox "The total is " & answer End Sub Here, we have changed the names in our Sub. The variable names are now different from the ones in the calling line They are now first2 and second2. But will it still work? Test your programme out and check it. You should find that it does. So to sum up, we can use a Sub to create our own code segment. We use this Sub just by referring to it by name. If we want to pass any values to our Sub, we can set up Parameters in between the parentheses. Exercise Create a Sub to check a Textbox for a valid email address, or adapt the one you already have. Pass whatever is entered in the Textbox to a variable called "email". Pass the value from this variable to your Sub by using a Parameter. When a button is clicked, a message box should pop up telling the user if the email address was wrong. In the next part, we'll take a look at those two curious terms, ByVal and ByRef. The word ByVal is short for "By Value". What it means is that you are passing a copy of a variable to your Subroutine. You can make changes to the copy and the original will not be altered. ByRef is the alternative. This is short for By Reference. This means that you are not handing over a copy of the original variable but pointing to the original variable. Let's see a coding example. Add a new button the form you created in the previous section. Double click the button and add the following code: Dim Number1 As Integer Number1 = 10 Call IncrementVariable(Number1) MsgBox(Number1) You'll get a wiggly line under IncrementVariable(Number1). To get rid of it, add the following Subroutine to your code: Private Sub IncrementVariable(ByVal Number1 As Integer) Number1 = Number1 + 1 End Sub When you're done, run the programme and click your new button. What answer was displayed in the message box? It should have been 10. But hold on. Didn't we increment the variable Number1 with this line? Number1 = Number1 + 1 So Number1 started out having a value of 10. After our Sub got called, we added 1 to Number1. So we should have 11 in the message box, right? The reason Number1 didn't get incremented was because we specified ByVal in the Sub: ByVal Number1 As Integer This means that only a copy of the original variable got passed over. When we incremented the variable, only the copy got 1 added to it. The original stayed the same - 10. Change the parameter to the this: ByRef Number1 As Integer Run your programme again. Click the button and see what happens. This time, you should see 11 displayed in the message box. The variable has now been incremented! It was incremented because we used ByRef. We're referencing the original variable. So when we add 1 to it, the original will change. The default is ByVal - which means a copy of the original variable. If you need to refer to the original variable, use ByRef. In the next part, we'll take a look at Functions in VB .NET A function is more or less the same thing as a Sub - a segment of code you create yourself, and that can be used whenever you want it. The difference is that a Function returns a value, while a Sub doesn't. When you Called a Sub you did this: Call AddNumbers(first, second) Visual Basic will go off and execute that code for you, and then drop down to the next line. The Sub AddNumbers is not a value, it's not equal to anything. It's not like a normal variable where you assign something to it. It's just the name of your Subroutine. A Function is different. It is a value, will be equal to something, and you do have to assign a value to it. You create a Function in the same way you did a Sub, but this time your code will be like this: Private Function ErrorCheck ( ) As Boolean End Function First, we've changed the word "Sub" to "Function"; second we've added "As" something, in this case "As Boolean". The name we called our Function is ErrorCheck, and ErrorCheck is now just like a variable. And just like a variable, we use one of the Types. We can use "As Integer", "As Long", "As Double", "As String", or any of the variable types. Let's write some code, and try an example. Add a new button and a textbox to your form. Change the Name of the textbox to txtFunction. Double click your button and add the following code to it (add it after the End Sub of the button, but before the End Class): Private Function CheckError ( ) As Boolean Dim TextBoxData As String TextBoxData = Trim(txtFunction.Text) If TextBoxData = "" Then MsgBox("Blank Text Box detected") CheckError = True End If End Function This is almost the same code from our Sub called ErrorCheck, in a previous section. The difference is the one added line - CheckError = True. Remember that CheckError is now like a variable. In this case it was a Boolean variable. So if there's nothing in the Textbox, we have set CheckError to True. Again, this code is not doing much good by itself. We need a way to use it. This time, because we've set up a Function, we have to assign the value of the function to a variable. Like this: Dim IsError As Boolean IsError = CheckError () Here, we are saying "Run the function called CheckError. When you have finished, assign the value of CheckError to the variable called IsError". Once that code is executed we can then use the variable IsError and test its value. If it's true, then we know that the user did not enter anything into the Textbox; if it's False, then we know that they did. The benefit of using a Function to check for our errors is that we can halt the programme if IsError = True. Like this: If IsError = True then Exit Sub End If So double click your button and add the following: Dim IsError As Boolean IsError = CheckError () If IsError = True then Exit Sub Else MsgBox("IsError = False") End If Run your programme again. Click the button when the textbox is blank, and see what happens. Then enter some text into the textbox, and click your button again. To sum up, then. A function will return a value. You put this value into the name of your Function. You then assign the value of the Function to a variable. You can then test the variable to see what's in it. In the previous section, you learned how to set up a simple function. Let's set up another Function, as a further example. This time we'll add some Parameters to our Function. You use the Parameters in exactly the same way as you did for a Sub. • So add another button to your Form • Set its Text property to "Get Function Answer" • Add two Textboxes to your Form • Set the Name Property of the first Textbox to txtNumber1 • Set the Name Property of the second Textbox to txtNumber2 • Set up the following Function in your code window (The first line might be spread over two lines here. You can keep yours on one line.) Private Function AddTwoNumbers(ByVal first As Integer, ByVal second As Integer) As Integer Dim answer As Integer answer = first + second AddTwoNumbers = answer End Function So the name of this Function is AddTwoNumbers, and we've set it up to return an Integer value. The two parameters we're passing in are also Integers. The code inside the Function simply adds up whatever is inside the variables first and second. The result is passed to another variable, answer. We then pass whatever is inside answer to the name of our Function. So AddTwoNumbers will be equal to whatever is in the variable answer. Instead of saying AddTwoNumbers = answer you can use the Return keyword. You use it like this: Return answer The result is the same: the value inside the variable answer is now the value of the function. Open up the code for your "Get Answer" button, and add the following code to it: Dim first As Integer Dim second As Integer Dim result As Integer first = Val(txtNumber1.Text) second = Val(txtNumber2.Text) result = AddTwoNumbers(first, second) If result = 0 Then MsgBox("Please try again ") Else MsgBox("The answer is " & result) End If So we're telling Visual Basic to execute our Function on this line: result = AddTwoNumbers(first, second) We're saying, "Run the Function called AddTwoNumbers. Hand it the values from the two variables. When you've finished running the function, pass whatever the value of AddTwoNumbers is to the variable called result." The next few lines are just testing what is inside the variable result. Remember: the variable result will hold whatever the value of AddTwoNumbers was. When you've finished typing your code, run your programme and test it out. Type a number in the first text box, and one in the other. Then click the "Get Function Answer" button. Try typing two zeros into the textboxes and see what happens. Setting up and using functions can be quite tricky at first, but it's well worth your while persevering: they can vastly improve your coding skills. In the next section, we explain what a Standard Module is, and how to create your own. The Subs and Functions worked perfectly well where they were - inside the two lines "Public Class Form1" and "End Class". If you tried to put them on a line underneath End Class you would get lots of blue wiggly lines under your code. That's because the code all belongs to Form1. But it doesn't have to. In fact, it's better to separate all your Functions and Subs and put them somewhere else - in something called a Module. We'll explore the Standard Module, and see how to move our Functions and Subs outside of Form1. That way, we can use them in other projects. So start a new project. Add a button to you new form. To add a Module to your project, click Project from the menu bar. From the from down menu, click on "Add Module": When you click "Add Module", you'll get the following dialogue box popping up: Select Module from the Templates window. Type a name for your new module - modVerify.vb. When you've typed a name, click the Open button. You'll should see a blank window, with this code in it: If you take a look at the Solutions Explorer on the right, you should see that your new module is listed: In between Module modVerify and End Module, type the following Subroutine: Private Sub AddNumbers(ByVal num1 As Integer) Dim answer As Integer answer = num1 + 10 MsgBox(answer) End Sub Your coding window should now look like this: Now click back on your form and double click the button you added. This will bring up the code window for the Form, and the cursor will be flashing inside of the button code. Add the following code for your button: Call AddNumbers(10) When you press the return key, you'll see a blue wiggly line under the Sub name. If you hold your mouse over AddNumbers, you might see this: Because this lesson is a bit long, we'll continue it on the next page. In the previous lesson, we saw that we had some problems with our code. VB placed a blue wiggly line under the name of our Sub: What VB is saying is that it can't see your new Subroutine from the inside of the button code. It thinks you haven't got a Sub called AddNumbers. The reason it can't see it is we made the Sub Private. Only code inside of the modVerify Module can see a Private Sub. If you want the Sub or Function to be available to all the code in your project, including the button, you have to make then Public. This involves nothing more than changing the word Private to Public. Amend your Sub to this: When you make the change from Private to Public, the blue wiggly line should disappear from the Button code Run your programme and test it out. Click your Button. You should get a message box saying "20". We'll now add a Function to our new Module. So bring up the code for your module. When you have your new Module displayed, type in the following Function: Public Function VerifyPostcode(ByVal postcode As String) As String postcode = StrConv(postcode, VbStrConv.UpperCase) Return postcode End Function When you're finished, your coding window should look like this: All the function does is to check a Postcode to see if the letters in it are all in capitals. That's because, quite often, people will enter a postcode as this: ts1 4jh What you want is a Postcode that reads: TS1 4JH The new function will convert a postcode handed to it, and make sure the letters are all capitals. The inbuilt function that does the converting is worth exploring. It's this: StrConv( ) This is short for String Conversion. In between the round brackets, VB needs you to put two things: the string you want to convert, and what sort of conversion you want. As soon as you type a comma after the string you want to convert, VB pops up a box of available conversion types: A lot on the list are rather baffling. But the one we used was the UpperCase one. Simple double click an item to add it to your code. This gave us the following: StrConv(postcode, VbStrConv.UpperCase) The function will then convert all the letters in postcode to capitals. Another useful one on the list is ProperCase. What this will do is take a string and convert all the letters of the first word (or words) to capitals. This is useful for addresses. So if somebody entered this as an address: 49 falkland street The VbStrConv.ProperCase item would convert it to this: 49 Falkland Street But back to our code. Select your Form again. Then add a new Button, and a Textbox to it. Change the Text property of the Textbox to ts1 4jh. Double click the button, and add the following code for it: Dim CheckPostcode As String Dim ConvertPostcode As String CheckPostcode = Trim(TextBox1.Text) ConvertPostcode = VerifyPostcode(CheckPostcode) TextBox1.Text = ConvertPostcode The first thing we do is get the Text from the textbox. This is passed to a variable called CheckPostcode. The next line calls our new function. We hand it the postcode we got from the textbox: ConvertPostcode = VerifyPostcode(CheckPostcode) When our function has finished the conversion, it will hand back (Return) the result and put it in the variable ConvertPostcode. This is then placed back inside the textbox. Run your programme, and click the new button. You should find that the letters in the postcode are converted to capitals. The point about creating a Module to house all your Subs and Functions is that they are in a separate file. You could write more Subs and Functions for your Module, ones that validate text coming from a textbox (an email checker, for example, or one that uses the ProperCase string conversion). You would then have all this code in one file that you could add to totally different projects. If the Subs and Functions were in the same code for the Form, you would have to import the whole Form before you could use the very useful Subs and Functions you created. But that's enough about Modules. We'll move on to a new section. What is an Event? An event is something that happens. Your birthday is an event. So is Christmas. An event in programming terminology is when something special happens. These events are so special that they are built in to the programming language. VB.NET has numerous Events that you can write code for. And we're going to explore some of them in this section. We'll start with all that mysterious code for the Button's Click Event. Exploring the The Click Event Buttons have the ability to be clicked on. When you click a button, the event that is fired is the Click Event. If you were to add a new button to a form, and then double clicked it, you would see the following code stub: Private Sub Button1_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) _ Handles Button1.Click End Sub This is a Private Subroutine. The name of the Sub is Button1_Click. The Event itself is at the end: Button1.Click. The Handles word means that this Subroutine can Handle the Click Event of Button1. Without the arguments in the round brackets, the code is this: Private Sub Button1_Click( ) Handles Button1.Click You can have this Button1_Click Sub Handle other things, too. It can Handle the Click Event of other Buttons, for example. Try this. • Start a New project • Give it the name it Events • When you new Form appears, add two Buttons to it • Double click Button1 to bring up the code • At the end of the first line for the Button, add this: Handles Button1.Click, Button2.Click Add a message box as the code for the Button. Your code window might then look like this: Run your programme, and then click both of the buttons in turn. The same message box appears, regardless of which one you clicked. The reason it did so was because the Events that the Button1.Click Subroutine can Handle are at the end: the Events for Button1.Click AND Button2.Click. You can add as many Events as you want on the End. As long as the Subroutine can Handle them, the Event will happen. For example, you could create two more buttons, and then add the Click Event on the end of the first button: Handles Button1.Click, Button2.Click, Button3.Click, Button4.Click When you click any of the four button, the code inside of the Button1_Click Subroutine will fire. However, if you double clicked button2 to try to bring up its coding window, you'd find that the cursor is flashing inside of the code for Button1_Click. Because you've attached the Click Event of button2 to the Button1 Subroutine, you can't have a separate Click Event just for Button2. This Click Event is Handled By the Subroutine called Button1_Click. Event Arguments The arguments for a Button's click event, the ones from the round brackets, are these two: ByVal sender As System.Object, ByVal e As System.EventArgs This sets up two variable: one called sender and one called e. Instead of sender being an integer or string variable, the type of variable set up for sender is System.Object. This stores a reference to a control (which button was clicked, for example). For the e variable, this is holding an object, too - information about the event. For a button, this information might be which Mouse Button was clicked or where the mouse pointer was on the screen. But because this is the Click Event, there's not much more information available: either the button was clicked or it wasn't. But you can use other Events available to the button. One of these is the MouseDown Event. The information for the event would be which button was clicked, where the mouse pointer was when the mouse button was held down, and something called Delta (a count of how many notches have been rotated on a mouse wheel). Let's explore the MouseDown Event. The MouseDown event is available to many controls on the form. A Form can detect when the mouse was held down on it; a textbox can detect when the mouse was held down inside of it; and a Button can detect which mouse button was held down to do the clicking. We'll see how it all works right now. First, delete the all but one of the buttons on your form. (You can right click on a control to delete it. If you haven't been following along from the previous lesson, then just create a new project. Add a Button to your form, and leave iton the default name of Button1.) Go back to your coding window, and delete any code for the button on your form. Delete any Handles code except for Handles Button1.Click. Your coding window should look something like this one: Right at the top of the code window, it says Button1 and Click. The lightning bolt next to Click signifies that it is an Event. If you click the drop down box, you'll see a list of other available events: Scroll down and find the MouseDown event, as in the image above. When you click on it, a new code stub appears, this one (it has been formatted so that the first line is spread over three lines): Private Sub Button1_MouseDown(ByVal sender As Object, _ ByVal e As System.Windows.Forms.MouseEventArgs) _ Handles Button1.MouseDown End Sub This is a Private Subroutine called Button1_MouseDown. Notice that it Handles the Button1 MouseDown event, and not Button1.Click. Exploring the Event Arguments In between the round brackets of the Subroutine, we still have ByVal sender As Object. But we have a new argument now: ByVal e As System.Windows.Forms.MouseEventArgs The name of the variable is still e. But the type of Object being stored inside of the e variable is different: System.Windows.Forms.MouseEventArgs The bit on the end of all that is what we're interested in: MouseEventArgs. This stands for Mouse Events Arguments. What is being stored inside of the e variable is information the Mouse Event: Did you click a button, if so which one? The only thing you need to do to detect which button was pressed is to access a property of the e variable. Let's see how to do that. Which Button was Clicked? Inside of the Button1_MouseDown Subroutine, type the following code: If e.Button = MouseButtons.Right Then MsgBox("Right Button Clicked") End If As soon as you type the letter "e", you'll see this pop up box: To detect which button was clicked, you need the first Property on the list: Button. Double click this property to add it to your code. Then after you typed the equals sign, another pop up list appears. This one: This is a list of available buttons that VB can detect. Left and Right are the ones you'll use most often. When you've added the If Statement, your coding window should look something like this: When you're finished writing your code, run your programme. Click the button with your Left mouse button and nothing will happen. Click it with the Right mouse button and you should see the message box display. MouseDown and the Form Stop your programme. When you are returned to the coding environment (Press F7 if you can't see your code), click the down arrow of Button1 at the top of the code. You'll see a drop down box like this: Select the one highlighted in the image, "Form1 Events". In the Events box to the right, select MouseDown from the list of available events. A new code stub will appear: Private Sub Form1_MouseDown(ByVal sender As Object, _ ByVal e As System.Windows.Forms.MouseEventArgs) _ Handles MyBase.MouseDown End Sub This time, we have a Private Subroutine called Form1_MouseDown. The two arguments are exactly the same as before. The difference is that now this code Handles the MouseDown event for something called MyBase. (This is an object that refers to the code for Public Class Form1.) The important thing to bear in mind is that we now have a way to detect when a mouse button was clicked on the form itself. Add the following code inside of Form1_MouseDown: If e.Button = MouseButtons.Right Then MsgBox("You clicked on the Form") End If The only thing that has changed is the Message Box! The If Statement is exactly the same. Run your programme and test it out. Click anywhere on your Form, and you should see the new message box. However, if you right click on the button, you'll get the old message box. Although the button is on the Form, this is considered a separate control from the Form itself. So it has its own events. You can detect where on the Form the mouse was when the right mouse button was click. Amend your code for Form1_MouseDown. Change it to this: Dim xPos As Integer Dim yPos As Integer If e.Button = MouseButtons.Right Then xPos = e.X yPos = e.Y MsgBox("The X Position is " & xPos & " The Y Position is " & yPos) End If First, we're setting up two integer variable, xPos and yPos. After that we have the same If Statement as before: If e.Button = MouseButtons.Right Then End If Inside of the If Statement, we're using the X and Y properties of the e variable: xPos = e.X yPos = e.Y The X property returns how far across, from left to right, the mouse is; the Y property returns how far down, from top to bottom, the mouse is. These values are assigned to our two variables. The result is displayed in a message box. When you've wrote the code, run your programme and test it out. Right click anywhere on your form. The new message box should display, telling you where the mouse was when the right button was held down. Click near the top of the form and you'll see the Y position number go down in value; Click near the bottom of the form and you'll see it go up in value. The very top of the form (or a control) has a Y value of zero. Click from left to right and you'll see the X numbers go up in value. The very left edge of your form has an X value of zero. In the next part, we'll explore the KeyDown event. Another useful event is the KeyDown event. As its name suggest, this allows you to detect when a key on the keyboard was held down. This is useful for things like validating text in a textbox. To test it out, add a textbox to your form. (If you haven't been following the lessons, just start a new project and add a textbox to your new form.). Change the Text property of the textbox to "Press F1 for help." Locate the TabIndex property in the Property Box, and change it to zero. (The Tab Index sets which control is selected when the Tab key is pressed on the keyboard. By specifying zero as the TabIndex property, you're saying that this should be the first control selected.) Bring up your code window (you can either click the tab at the top, or press F7 on your keyboard), and click the arrow that reveals the list of controls and objects in your project: Click on your textbox from the list to select it, as in the image above. Then click the arrow on the Event drop down box to reveal the events available to the textbox. Scroll down and select the KeyDown event: When you select the KeyDown event, a code stub appears: Private Sub TextBox1_KeyDown(ByVal sender As Object, _ ByVal e As System.Windows.Forms.KeyEventArgs) _ Handles TextBox1.KeyDown End Sub The event that is being Handled is the KeyDown event of TextBox1. Notice, though, that there is a slightly different argument in round brackets: ByVal e As System.Windows.Forms.KeyEventArgs Again, the variable name is still e. But now we have something called KeyEventArgs on the end. This means that the variable e will hold information about the Key on the keyboard that you're trying to detect. To see what properties the e variable has available to it, add the following to your TextBox1_KeyDown code: If e.KeyCode = Keys.F1 Then TextBox1.Clear() MsgBox("Help!!!") End If As soon as you type the full stop after the letter "e", you'll see this pop up box: Double click a property to add it to your code. After you type an equals sign, you'll get another pop up box: The list is a list of keys on your keyboard, some of which you'll have and others that you won't. Scroll down the list until you come to Keys.F1, and double click the item to add it to your code. The code for the If Statement just clears the textbox and pops up a message. Try your programme out. Press F1 (If you set TextIndex to zero then the text in the textbox should be selected, and the cursor already flashing. If it's not, click inside of the textbox and then press F1). When the F1 key is pressed, you should see the message box appear. Another thing you can do is to record the keystrokes a user makes. For example: Dim RecordText as String RecordText = RecordText & Chr(e.KeyCode) MsgBox(RecordText) The Chr( ) function converts a KeyCode (which is an integer) to its keyboard character. But try this exercise. Exercise There is an event available to the textbox called Leave. Add another textbox to your form, and write code so that the letters in a postcode are converted to uppercase when the user clicks from your first textbox and into your second textbox. So your first textbox might read "ts1 4jh". When the user clicks inside textbox2, the text from textbox1 should change to "TS1 4JH". The code can be written in the Leave event of textbox1. There are an awful lot of Events to explore, and we'll have a look at just one more - the Form Load Event. We'll do that in the next part. An important event you'll want to write code for is the Form Load event. You might want to, for example, set the Enabled property of a control to False when a form loads. Or maybe blank out an item on your menu. You can do all this from the Form Load event. Add another button to your form for this example, and we'll see how the Form Load event works. (If you haven't been folowing along, create a new project and add two buttons to it. Bring up your coding window, and select the Form1 Events from the drop down box: In the events drop down box, select Load. A code stub for the Form Load event is then added to your code. Type in the following as the code for the Load Event: MsgBox("Form Load Event") Run your programme. You should see the message box display before the Form loads. To switch off your second Button before the Form loads, add this to your code: Button2.Enabled = False Run your programme again. You should see that button is no longer available for clicking on. We'll now up the pace a bit. We'll have a look at just what Objects are, and how you can create your own. VB.NET is an Object Oriented programming language. The Objects referred to are created from something called a Class. You've already used Classes throughout this course. But we'll now have a closer look at them. Object Oriented programming The modern trend in programming languages is for code to be separated into chunks. When it's being used, each chunk of code (a chunk of code that opens text files, for example) is known as an Object. The code for the Object can then be reused whenever it is needed. Languages like C++ and Java are Object Oriented languages. Until Microsoft came out with VB.NET, the Visual Basic programming language was not OOP (object oriented programming). This time it is. Object Oriented programming has a steeper learning curve, and things like Encapsulation, Inheritance and Polymorphism have to be digested. We're not going quite that far in this beginner's course. But you should have a good, basic understanding of just what Object are by the end of this section, and how to create your own Objects. Classes and Objects In VB.NET, a class is that chunk of code mentioned earlier. You've been using Classes all the time during this course. The Form you've started out with is a Class. If you look right at the top of the code window for a Form, you'll see: Public Class Form1 The word "Public" means that other code can see it. Form1 is the name of the Class If you look at the bottom of the coding window, you'll see End Class, signifying the end of the code for the Class. When you place a Button or a textbox on the Form, you're really adding it to the Form Class. When you start the Form, VB does something called instantiation. This basically means that your Form is being turned into an Object, and all the things needed for the creation of the Form are being set up for you (Your controls are being added, variables are being set up an initialised, etc). And that's the basic difference between a Class and an Object: A Class is the code itself; the code becomes an Object when you start using it. The NET Framework The NET Framework is something that Microsoft have invested a lot of time, effort and money into creating. It's big. Very big. The way that programming will be done on a Microsoft machine from now on is with NET. And not just on a Microsoft machine. There's something called ADO.NET which is used for creating web site, and for manipulating databases. You can create applications for mobile phones and PDA's with NET. There is even a project in the making that will allow you to write a programme on a Windows machine that will then work on a computer NOT running Windows. All this is made possible with the NET Framework. But what is it? The NET Framework is a whole lot of Classes (called Namespaces) and the technology to get those Classes to work. The main component is called the Common Language Runtime. A Runtime is the thing that gets your code to actually run on a computer. Previously, these Runtime Languages were machine or programming language specific. The Runtime that gets a Java programme to work, for example, is different to the one that gets a C programme to work. With NET, more than 15 different programming languages can use the Common Language Runtime. One of these languages is, of course Visual Basic NET. Another is C# (pronounce C Sharp). They can all use the Common Language Runtime because of something called the Intermediate Language. (This is a sort of translator for the various languages, and is too advanced to go into for us.) Namespaces A Namespace is a group of Classes which are grouped together. The System.IO Namespace you met earlier groups together Classes that you use to read and write to a file. System.Windows.Forms is another Namespace you've met. In fact, you couldn't create your forms without this Namespace. But again, it is just a group of Classes huddling under the same umbrella. System itself is a Namespace. It's a top-level Namespace. Think of it as the leader of a hierarchy. IO and Windows would be part of this hierarchy, just underneath the leader. Each subsequent group of Classes is subordinate to the one the came before it. For example Forms is a group of Classes available to Windows, just as Windows is a group of Classes available to System. A single form is a Class available to Forms: System.Windows.Forms.Form The dot notation is used to separate each group of Classes. A Button is also part of the Forms Class: System.Windows.Forms.Button As too is a Textbox: System.Windows.Forms.TextBox The leader of the hierarchy is still System, though. Think of it as an army. You'd have a Private who is subordinate to a Sergeant. The Sergeant would be subordinate to a Captain. And the Captain would be subordinate to a General. If the General wanted something done, he might ask the Captain to do it for him. The Captain would get the Sergeant to do it, and the Sergeant would then pick on a poor Private. So Button would be the Private, Forms would be the Sergeant, Windows would be the Captain, and System the General. In other words, there is a chain of command in NET programming. And if you don't follow the chain of command, you're in trouble! But you see this chain of command every time you type a full stop and a pop up box appears. When you're selecting an item from the list, you're selecting the next in the chain of command. This code at the top of the form window: Inherits System.Windows.Forms.Form means you don't have to keep typing the full chain of command every time you want to access a button on the form. This chain of command is inherited whenever you create a new VB.NET Form. There are plenty of times when a chain of command is not inherited though, and in that case you do have to type it all out. You did this when you referenced a StreamReader with: System.IO.StreamReader The IO Namespace is not inherited when you created a new Form, so you have to tell VB where it is in the hierarchy. But that's not quite the end of the story. The reason you using all of these long Namespaces is to get at a Property or Method - the chaps that do all the actual work! When you type Button1.Text = "Click Me", Text is a Property of Button1. Button belongs to Form, which belongs to Forms, which belongs to Windows … etc. So whenever you access a Property or Method of a control, just remember that rather long chain of command. In the next part, you'll learn how to create your own Classes If you haven't yet read the introduction to Classes, here it is: VB .NET Classes and Objects. The big benefit of an Object Oriented Programming language is that you can create your own Objects. (It's an Object when you're using the code, remember, and a Class when you're not.) We'll see how to do that now, as we create a very simple Class, and then turn that into an Object. The Class we'll create is a very simple one, and is intended to show you the basic technique of setting up a Class, then creating an object from it. The Class we'll create will convert the letters in a postcode to uppercase. We'll get the postcode from a textbox on a form. Off we go then. • Start a new VB .NET project • Add a Textbox to your form, and leave it on the default Name, Textbox1 • Change the Text Property to ts1 4jh (make sure the letters are lowercase and not upper, because our object will convert it.) • Add a Button to your form Once you have a new form with a Textbox and a Button on it, you need to add a Class. This is quite easy. It's just like adding a Module. In fact, they look exactly the same! • So from the VB menu bar, click on Project • From the drop down menu, click Add Class • You'll get this dialogue box popping up: The Class Template on the right will already be selected. The thing you need to change is the Name at the bottom. The default Name is Class1.vb. This is not terribly descriptive, and you'll have great problems working out what this class does, a few months down the line. Change the Name from Class1.vb to ConvertPostcode.vb. Then click the Open button. When the code window for the class opens up, it will look like this: As you can see, there's not a great deal to look at! All we have is the Public Class … End Class code stub. The name of our Class is also there. But the code is in a separate window, and has a tab all to itself. It's this tab full of code that you reuse and turn into an object. What we have to do now is add the code that does the work - converts our postcode. But we can't just write this: Dim ConvertPostcode As String ConvertPostcode = StrConv(TextBox1.Text, VbStrConv.UpperCase) TextBox1.Text = ConvertPostcode That would be all right for the button on our Form. But it's not all right for our Class. When you're designing a Class, your code has to go inside of things like Functions and Subs. You'll also see how to create your own properties for your objects. When you set up a Function or Sub, you're actually creating Methods for your objects (A Method is code that actually does something, that performs an action. Converts a postcode in our case.) We'll see how to do that next. A method created in a Class is nothing more that a Function or a Sub. You've seen how to do this in an earlier section. The process is the same. So add the following code to the Class you created for the previous lesson: Public Function DoConvert(ByVal postcode As String) As String Dim ConvertPostcode As String ConvertPostcode = StrConv(postcode, VbStrConv.UpperCase) DoConvert = ConvertPostcode End Function When you've finished typing it all, you Class should look like this in the code window: All we've done is to set up a Public (not private) function. We've given it the name "DoConvert". We've set it up to accept one parameter, a String variable called postcode. This is the value that will be handed to our function. The function itself has been set up as a String. This means that DoConvert will be just like a string variable that we can assign a value to. The code itself you've met before. It uses the in-built StrConv function to do the actual job of converting the string to uppercase letters. Now that we've set up a Method, let's see how to create an object from our Class, and put the Method to use. Creating an Object from a Class Our function is not much use until we can get it up and running. (Here, "Get it up and running" means create an object from our class.) To do that, double click the button on your Form, and add the following code to it: Dim NewCode As String Dim objConvertPostcode As ConvertPostcode objConvertPostcode = New ConvertPostcode NewCode = objConvertPostcode.DoConvert(TextBox1.Text) TextBox1.Text = NewCode The first line just sets up a new String variable called NewCode. Whatever is returned from our function will be stored inside of this variable. The next line is where the action starts: Dim objConvertPostcode As ConvertPostcode The variable name objConvertPostcode is just something we made up ourselves. The "obj" prefix means Object, and this is for our benefit, to remind us that the type of data inside it holds an Object, rather than a plain old Integer or String. After you type the word "As", then hit your spacebar, you'll see s popup box appear. If you type the letters "conv", you'll see the list automatically move down. The Class your created should be on that list, as in the next image: You can double click the name of your Class to add it to your code. But what you're doing in this step is setting up a pointer to your Class. You're telling VB where the Class can be found, and then storing this inside of the variable called objConvertPostcode. If VB doesn't know where your Class is then it can't create an Object from it. The next line of code is the one that creates a new object from your Class: objConvertPostcode = New ConvertPostcode You type the Name of your variable first, then an equals sign. To the right of the equals sign comes the word "New". This is what tells VB to create a New Object. And the class its creating the New Object from is the one called ConvertPostcode. You can actually type all of that on the same line: Dim objConvertPostcode As ConvertPostcode = New ConvertPostcode This does two jobs: sets a pointer to where the Class is, and creates a new Object from the Class. But there's reasons why you don't want to do it this way. One is that Objects take up space in memory. And you only really need to create them when they are needed. For example, what if the textbox was blank? You'd want to check for this and invite the user to try again. If you've written everything on one line, then you've already created the Object before the Textbox has been checked. Instead, you could do something like this: If TextBox1.Text = "" Then MsgBox "Please try again" Exit Sub Else objConvertPostcode = New ConvertPostcode End If Here's, the textbox is being checked first. If the user has left it blank then we bail out. If not, THEN we create an Object from our Class. The next line in our code was this: NewCode = objConvertPostcode.DoConvert(TextBox1.Text) First, we type the name of the variable we want to store the result of our Method into. In our case, the one called NewCode. After the equals sign, we type the name of our Object variable: objConvertPostcode As soon as you type a full stop after your Object variable, you should see a popup box with the name of your new method on the list: The image above shows you that the name of our Method "Do Convert" has been recognised by VB. (You can tell it's a Method because of the purple block next to it.) But notice the tool tip - it's the first line from our Function! In between the round brackets, VB is telling us what type of data needs to be passed over to the Method - a String of text. The second "As String" tells you that the Method returns a value that needs to be stored somewhere. So if you've set up a Method that returns a value (a Function) then you need to store it in a variable. To get at the Method inside of your class, first type the name of your Object variable. The type a full stop. Look for the name of your Method in the pop up list that appears. The final line of the code just assigns the value returned from the Method back to the textbox: TextBox1.Text = NewCode Run your code and test it out. Click your Button and you should see the postcode change from "ts1 4jh" to "TS1 4JH". In the next part, we'll study the subject of creating Methods some more. In the last part, you created a Method that returned a value. But you Methods do not have to return a value. In which case, you create a Sub and not a Function, like we did the last time. Add the following code to your Class: Public Sub DoMessageBox() MsgBox("Conversion Complete") End Sub This is a Public Sub that doesn't do anything terribly useful. But it will illustrate how to write code to set up a Method that doesn't return a value. Here's what your coding window should look like: To run your new method, return to your Button code. You should have this, remember: On a new line after Textbox1.Text = NewCode, type the following: objConvertPostcode.DoMessageBox() After you type the name of your Object variable, then a full stop, you get the message box popping up. This time, your new Method is on the list: The tip next to the pop up box is telling you that the Method is a Sub, and that it therefore doesn't return a value. The Sub also has no parameters inside of the round brackets, so you don't have to hand anything to it. You can double click the new Method to add it to your code. When you press the return key on your keyboard, VB adds a pair of round brackets to the end of the line. So calling a Method that doesn't return a value is just like calling a Sub. The difference is that you need the name of your Object variable first. If we had set up the Sub inside of the Form1 code, we would have just done this to call it: DoMessageBox() But because the Sub was inside of the Class, you first type the name of your Object variable: objConvertPostcode.DoMessageBox() Run your code again. Click your button. You should see two things happen: one, the text in the textbox will change; and two, you should see message box popping up confirming the change. Now that you know how to create Methods for your Classes, in the next part you'll see how to create your own Properties. In the previous sections, you have learned how to create a Class in VB .NET. You also learned how to create your own Methods. In this part, you'll learn how to create your own properties. Creating your own Properties in VB .NET Classes You can add your own Properties to your Class. A Property, remember, is something that changes or sets a value. Examples are, setting the Text in a textbox, changing the background colour of a Form, and setting a Button to be Enabled. You can Get values from a Property or Set them. So for a Textbox, you can Set the text to appear in the textbox, or you can Get what text is inside of the textbox. You use these same words, Get and Set, when you're creating your own Properties. An example might clear things up. In this example, we'll allow users to set the height and width of an image. These values will come from textboxes on a form. Before you do the following, Once you have the images on your hard drive, do the following: • Start a new project • Add a Picture Box control to your Form • Set the SizeMode Property of the Picture box to StretchImage • Click on the Image Property, and add the planet.jpg image that you downloaded above • Add two textboxes to the form. Change the Name of the first one to txtHeight, and the second one to txtWidth. Enter 300 as a the text for both textboxes • Add two labels to the form. Set the Text of the first one to Height, and the second one to Width. Move them next to the textboxes • Add a new button to your form. Set the Text property to “Change Height and Width” You now need to add a new class. So from the menu bar, click Project. From the Project menu, select Add Class. Give it the Name of changeHeightWidth.vb. Click the Add button, and you'll be taken to the coding window for your new Class. VB now needs to know that you want to set up a Property for your Class. The way you do this is type "Public Property … End Property". On a new line, and before End Class, type the following: Public Property ChangeHeight() As Integer ChangeHeight is the name of our property, and it's something we made up ourselves. After a pair of round brackets, you add the type of value that will be returned (Just like a function). Here, we want to return an Integer value. When you press the return key after typing that line, VB finishes off the rest of the code stub for you: Public Property ChangeHeight() As Integer Get End Get Set(ByVal Value As Integer) End Set End Property Before the code is explained, add a new variable right at the top of your code, just below "Public Class changeHeightWidth". Add this: Private intHeight As Integer The Private word means that only code inside of the Class can see this variable. You can't access this code directly from a button on a Form, for example. The reason the variable is right at the top is so that other chunks of code can see and use it. But your coding window should now look something like this next image: With the Get and Set parts, the Property stub is this: Public Property PropertyName( ) As VaraibleType End Property The reason the Get and Set are there is so that you can Set a value for your property, and get a value back out. To Set a value, the code inside of Property is this: Set(ByVal Value As Integer) End Set The Set word is followed by a pair of round brackets. Inside of the round brackets is ByVal Value As Integer. The is just like a Sub, when you hand over a value to it. The name of the variable, Value, is a default name. You can change this to anything you like. The type of variable, As Integer, is also a default. You don't have to pass numbers to you property. If you want your Property to handle text you might have something like this: Set(ByVal MyText As String) But you couldn't do this: Set(ByVal Value As Integer, ByVal MyString As String) In other words, you can't pass two values to your property. You can only pass one value. But we want to pass a number to our property. For us, this value will come from the textbox on the form. Whatever number is inside of the textbox will get handed over to our Property. Set(ByVal Value As Integer) But we need to use this value being handed over. We can assign it to that variable we set up at the top of the Class. So add this to your code (The new line is in bold): Set(ByVal Value As Integer) intHeight = Value End Set Whenever our Property is called into action, we're setting a Value, and then handing that value to a variable called intHeight. This is known as Writing to a Property. To read from a Property, you use Get. This will Get a value back out of your Property. The code stub is this: Get End Get You don't need any round brackets for the Get part. You're just fetching something to be read. Add the line in bold text to your Get statement. Get ChangeHeight = intHeight End Get All you're doing here is returning a value, just like you do with a function. You're handing a value to whatever name you called your property. We called ours ChangeHeight. It's an Integer. So we can pass whatever value was stored inside of intHeight over to the variable called ChangeHeight: ChangeHeight = intHeight You can also use the Return keyword. Like this: Get Return intHeight End Get Let's see how to use our new Property. (It's not a terribly useful property, by the way. A Picture box already has a Height and Width property that you can use. So ours is a bit redundant. But we're keeping it simple so that you can understand how to create your own properties.) The property you have just created is not much good where it is. You need to be able to call it into action. The way you do that is to create a new object from the Class, and then read and write to your property. So double click the new button you added to your form. Add the following code to it: Dim objAlterPicBox As changeHeightWidth Dim NewHeight As Integer objAlterPicBox = New changeHeightWidth Two of the line you've already met: the one that creates a pointer to a variable (the first line), and the one that creates a new Object from your Class (the third line). The second line just sets up a variable called NewHeight. To pass a value to your new Property (the Set part), add this line: objAlterPicBox.ChangeHeight = Val(txtHeight.Text) As soon as you type the name of your object variable, then a full stop, you'll see the pop up box appear: The image above is from the VB NET Express edition. Other users may see a different image. But your property will still be on the list. (You can tell it's a Property because the symbol next to it is a hand holding a card.) If you double click the Property, the code is added for you. After typing an equals sign, you then assign a value to your new property. Here, we're just passing the property whatever value is inside of the textbox called txtHeight. But we need to Get a value back out, so that we can do something with it. The way you Get at values is to put your code that accesses the property on the right hand side of an equals sign. On the left, You need the name of a variable. So add the following to your code: NewHeight = objAlterPicBox.ChangeHeight So whatever value was stored inside of ChangeHeight (or Returned), Gets handed over to the NewHeight variable. You can then set the height of the picture box: PictureBox1.Height = NewHeight When you add that line above, your Button code should look like this: Notice the last line: objAlterPicBox = Nothing Because objects take up space in memory, you can release them by setting the object to Nothing. VB is supposed to do the cleaning up for you, but you can't be sure that it's doing its job properly. So it's good form to release your own objects from memory. When you've finished adding the code, run your programme and test it out. Click your new button and the Height of the picture box should change. So just to recap: • You set up a Property by using the following code stub: Public Property PropertyName( ) As VaraibleType Get End Get Set(ByVal Value As Integer) End Set End Property • The Set Statement is for setting values for your properties • The Get Statement is for returning values from your properties • Once you’ve created a new object variable to use you class, type the name of the variable and select your property from the pop up list • When you’re setting values for your property, the object variable and property go on the left hand side of the equals sign ObjectVariableName.PropertyName = PropertyValue • When you’re getting values from your property, the object variable and property go on the right hand side of the equals sign VariableName = ObjectVariableName.PropertyName • Release your objects from memory by using the Nothing keyword OK, that’s just about it for this introduction to Classes and Objects. There’s an awful lot more to learn about Objects, but as a beginner you have learned the fundamentals.. Before you leave this topic, try this exercise: Exercise Set up a property that changes the width of the Picture Box on your Form. Get the new width from the second textbox on your Form. In the next section, we take a look at VB .NET and Databases. In this section of the course, we'll take a look at some of the extra things you can do with VB.NET forms. First, we'll take a look at the Anchor and Dock properties of a form. Anchoring and Docking The Anchor and Dock properties of a form are two separate properties. Anchor refers to the position a control has relative to the edges of the form. A textbox, for example, that is anchored to the left edge of a form will stay in the same position as the form is resized. Docking refers to how much space you want the control to take up on the form. If you dock a control to the left of the form, it will stretch itself to the height of the form, but its width will stay the same. Let's take a look at some examples, to clear things up. Anchoring Start a new windows projects. Add two textboxes to your form, and set the MultiLine properties of both to True. Change the height of the boxes. Click on Textbox1 and locate the Anchor property in the Properties box: The default is to anchor the control to the Top, Left edge of the form. Click the arrow to reveal a curious drop down box: The button in the middle represents your control. The big white areas are rather confusing - they don't actually do anything! To change the property, you click the smaller grey or white rectangles between the big white rectangle. Click again to deselect it. In the image below, the property has been changed so that the textbox is anchored to the Top, Left and Right sides of the form: The next image has the textbox anchored to the Right and Bottom edges of the Form: Notice where the cursor is in the images, and what has been changed. Click the arrow on the drop down box to confirm your choices. To see what effect this all has, do the following: • Set the Anchor property of Textbox1 on the default of Top, Left • Change the Anchor property of Textbox2 to None (all the small rectangles should be white.) • Run your programme and drag the edges of the Form outward. This will resize your form What you should notice is that Textbox1 stays where it is, and that the left edge of Textbox2 moves. Stop your programme from running. Change the Anchor properties of the two textboxes to anything you like. Run your form again and watch what happens. Try anchoring one textbox to the left and right of the form. Watch what happens. But anchoring a control to an edge of the form is a useful property to get used to, if you have a form that can be resized and want your controls to stay where they are. Docking Docking is similar to Anchoring, but this time the control fills a certain area of the form. To see how it works, click on one of your textboxes and locate the Dock property. Click the arrow to reveal a drop down box: This time, all the rectangles are like buttons. You can only dock to one side at a time, and the default is None. Click a button to see what it does to your textbox. Click the middle one, and the textbox will Fill the whole form. Docking is quite useful when used with the splitter control and panels, allowing you to create a Windows-style interface. The toolbar is a very popular and much-used addition to a programme. It's difficult to think of a piece of software that doesn't make use of them. VB.NET lets you add toolbars to your forms, and the process is quite straightforward. Let's see how it's done. Adding a Toolbar Either start a new Windows project, if your prefer (or have just joined us), or keep the one you currently have from the previous section. To add a toolbar to the top of your form, expand the Toolbox and locate the Toolbar control (you may have to scroll down to see it.) Double click the Toolbar control, and it will be added to the top of your form. However, there's not much to see, at the moment. Toolbars work by adding buttons and images to them. The button is then clicked, and an action performed. Click on your Toolbar to select it. In the property box for the Toolbar, you'll notice that it has the default Name of ToolBar1. We'll keep this Name. But locate the Buttons (Collection) property, and click the button with the three dots in it. This brings up the ToolBarButton Collection Editor. To add a new button to your toolbar, click the Add button: Each button on the toolbar has it's own properties and methods. The button you have just added has a default Name of ToolBarButton1. This is not terribly descriptive. What we're going to do is add three toolbar buttons: one to create a new file, one to open a file, and one to save a file. So, • Click the Name property and change it to tbrFileNew • Click Add to create a second button • Change the Name of this to tbrFileOpen • Add a third button and change the Name property to tbrFileSave • Then click OK • Your toolbar will look like this: The buttons, however, might look a bit small. You can change the height and width of them by clicking the Toolbar control to select it. Then locate the ButtonSize property in the properties box. When you've located the ButtonSize property, change the height and width of your buttons to 32: Adding Images to your Toolbar Buttons But your toolbar buttons are not much good as they are. Toolbar buttons usually have a picture on them. Ours are all blank. The toolbar buttons get their pictures from the Image List control. You add pictures to the Image List, then point your toolbar at this control. The toolbar will then recognise the images in the list. So expand the Toolbox, and scroll down until you find the ImageList control. Double click it to add one to your project. The ImageList is another control that doesn't appear on the form, but in the area below it: The shaded area around the control means it is selected. Once you have selected the ImageList control, locate the Images property in the properties box. Click the button with the three dots on it to bring up the Image Collection Editor. Again, you click the Add button to add images to the Collection. There are a few 16 by 16 pixel bitmap images to try out. When you click the Add button, navigate to this folder where your Bitmaps are, and select the image called fileNew.bmp. The image will be added to this list, and your dialogue box will look like this: Add the images called fileNew.bmp and fileSave.bmp to the Images Collection, then click OK. You now need to point the toolbar at these images. So click on your Toolbar to select it. In the properties box, locate the ImageList property. Click the arrow, and select your ImageList from the drop down box: Your Toolbar will now recognise your images. To add an image to a button, scroll up to the Buttons property and bring up the ToolbarButtons Collection Editor again. With the first button selected, locate the ImageIndex property, and click the arrow. You'll see a list of the images you added to the Image List: Select the first one. This image will then be used as the icon for toolbar button 0. Click on your next button under Members, and add image 1 from the ImageIndex list. Click on your third button, and select the final image, number 2. Then click OK. Your toolbar will then look like this: The images look a bit small, though. To increase the size of the image, click on your Image List at the bottom to select it. Locate the ImageSize property, and change the Height and Width property to 32 pixels. (Note: We could have also changed the ButtonSize Height and Width properties of the toolbar to 16 by 16. But let's make them nice and big!) Run your programme and see what your new toolbar looks like. Of course, if you click on the buttons nothing will happen. We need to write the code that gets them to work. Coding for your Toolbar Buttons Return to the Design environment. Double click your toolbar to bring up the coding window. It should look like this: Note the second line above (it's only the second line because we used the underscore character to spread the line out a bit, so that it would fit on this page). There's a variable called e, and the Click Event Arguments of the toolbar are being assigned to it. What this means to you is that the code you have to write is fairly straightforward. Add the following code in between Private Sub … and End Sub: If e.Button Is tbrFileNew Then MsgBox("File New Button Clicked") End If As soon as your type the letter e and a full stop, you get a list of available arguments. One of these is Button. In the If statement, we're just checking if the Button that was clicked Is the button called tbrFileNew. If it is, we'll just display a message box. But in reality, you'll probably want to call a Sub or function that executes some code here. Or just add the code itself. You can add more If Statements to check for the other buttons. In the image below, we've used If .. ElseIf Statement. The toolbar is a very popular and much-used addition to a programme. It's difficult to think of a piece of software that doesn't make use of them. VB.NET lets you add toolbars to your forms, and the process is quite straightforward. Let's see how it's done: Adding a Quick Toolbar There's a very easy way to add a toolbar in Visual Basic 2005 Express. Try this: • Start a New Project • When the form loads, expand the Toolbox on the left hand side • Look for the ToolStrip Control: • Double click the ToolStrip item to add it to your Form When you double click the ToolStrip, two things happen. The top of your Form will change to this: And a ToolStrip control will appear on the yellow area at the bottom of the screen: To add quick Toolbar, have a look at the Properties box on the right hand side, and locate this area at the bottom: • Click Insert Standard Items. Your Form will then look like this: As you can see, a default set of buttons appear on the toolbar. You've seen these so many times that there's no need to explain what they do. However, you may not want all of these items on your toolbar. Or any of them. So how do you add your own Images? We'll find out in the next part. Before you go on, click Edit > Undo from the VB .NET menu bar. This will remove the default items. If you haven't already done so, add a ToolStrip control to a new VB .NET Form. In the previous section, you saw how to add a quick toolbar. This inserted some default buttons and images for you. In this part, we'll see how you can add your own buttons and images. Add a Toolbar with VB 2005 Express Edition With your ToolStrip1 control selected, do the following: • Locate the Items (Collection) property in the Properties box for ToolStrip1, and click the button: When you click the button, it will bring up the Items Collection Editor. From here, you can add buttons and images for your toolbar. • Make sure the drop down box at the top says ToolStripButton: • Click the Add button to add a button to your Toolbar: However, this will get you an image and some text. We don't want the text, so locate the Display Style property on the right hand side, and change it to Image: Next, locate the Text Property and delete the default text (ToolStripButton1). The Text property should be blank. To add an image, click the button on the Image property: When you click the button, you get another dialogue box popping up. This is where you can search for an image for your button. So click the Import button at the bottom of the Select Resource dialogue box. Locate the Bitmap images you downloaded above. And select the fileNew Bitmap. Click Open. Then click OK on the Select Resource dialogue box. Your will be returned to your Items Collection Editor. Add two more buttons in the same way. For the images, add the fileOpen and fileCopy bitmap images. The Items Collection Editor should now look like this: You can add a separator to your toolbar. This separates your buttons. So click the drop down list, and select ToolStripSeparator. Then click the Add button. Go back and select ToolStripButton from the drop down list. Add the fileSave and filePrint Bitmap images exactly as you did above. The Items Collection Editor will then look like this: When you're done, click OK on the Items Collection Editor dialogue box. If you got everything right, your form will look like this one: Press F5 to run your programme. The toolbar should look like this: Coding for your Toolbar Buttons The coding for Toolbar Buttons is the same as for any buttons • Stop your programme running • With the Form displayed, double click a button to bring up the code window • Add this for the Click event: Run your programme again and click the Toolbar button you added code for. You should see the message box display. Of course, you would want to actually do something a little more useful than this: you'd probably want to call a function that opens a file, saves it, creates a new document, etc. These are covered elsewhere in the course. In the next section, we'll move on and have a look at how to create more than one form in your project t's a rare programme that only has one form in it. Most programmes will have other forms. These other forms can be used for things like Find and Replace searches, extra formatting capabilities, to set Options for the programme, and a whole lot more besides. VB.NET let's you add as many forms as you want to your project. But the process is not quite so simple. We'll see how to do it, though. • Start a New project • This will create a form called Form1 • To create a second form, click the Project menu • From the drop down menu, click Add Windows Form • The Add New Item dialogue box appears: Select Windows Form under Templates. Then click inside the Name textbox at the bottom. Change the Name of the form to frmSecond.vb. Then click Open. When you are returned to the design environment, your new form will be displayed: To switch between forms, you can click the tabs. In the image, two tabs are displayed: Form1 (the original and first form), and our new form frmSecond. We'll write code to get this new form to display. But it will only appear when a button is clicked on Form1. So click the tab for Form1, and add a button to this form. Change the Name property of the button to btnShowSecond. Then double click the button to access the code for it. The old way to display a Form was this: frmSecond.Show You can still do this in the VB 2005 Express Edition. But that's not the modern way. The modern way is to create a new object from a Form class. Then call its Show method. So add this code to your button: Dim SecondForm As New frmSecond SecondForm.Show() The first line sets up a variable called SecondForm. When you type "As New", you're asking VB.NET to create a New object. If you type a space, you'll see a pop up list. Type the frm of frmSecond and you should see it displayed on the list. You can double click the item in the list to add it to your code. But what the line does is create a new Object from the Class called frmSecond. Once we have the Form Object stored in the variable, we can just use the Show method to display the form. Run your programme and test it out. When you click your button, you should see the second form appear. However, there's a problem with this code. Click the button again and another copy of frmSecond appears. Keep clicking the button and your screen will be filled with the second form! To prevent this from happening, you can move the code that creates the form object. Move it right to the top of the coding window, just below Inherits System.Windows.Forms.Form (Visual Studio users. For VB Express, move the first line of code to just below where it says Public Class Form1 - outside of the button, in other words). The only code left in the button is the line that Shows the form. A new form object will now not be created every time the button is clicked. If you try it out, you should see only one form appear when the button is clicked, and not multiple forms. In the next part, we'll take a look at Modal and Non Modal forms. A modal from is one that has to be dealt with before a user can continue. An example is the Change Case dialogue box in Microsoft Word. If you try to click away from the dialogue box, you'll here a beep to indicate an error. Until you click either the Cancel or OK buttons, the programme won't let you click anywhere else. The second form you've just created is called a Modeless form. These are forms than can be hidden or sent to the taskbar. You can then return to the main form or programme and do things with it. A Modal form is sometimes called a dialogue box. And we'll see how to create one of these now. Add a second button to your Form1. Change the Name property of the new button to btnDialogueBox. Double click the new button and add the following code: Dim frmDialogue As New frmSecond frmDialogue.ShowDialog() To display a form as a Modal dialogue box, you use the ShowDialog method. If you use the Show method, the form is displayed as a Modeless form. Run your programme. Click your new button, and the second form should display. Move it out the way and try to click a button on Form1. You won't be able to. The second form has to be dealt with before you can access Form1. When the form is a Modal dialogue box, you can create OK and Cancel buttons for it. VB.NET then has a trick up its sleeve for these types of buttons. We'll see that trick now. OK and Cancel Buttons In the design environment, Click the Tab for your frmSecond. When the form is displayed in the design window, add two buttons to it (Make sure you're adding the buttons to the second form and NOT Form1). Change the Name property of the first button to btnOK, and the Name property of the second to btnCancel. Double click your OK button and add the following code to it: Me.DialogResult = DialogResult.OK The Me keyword refers to the current form. When you type a full stop, select DialogResult from the pop up list that appears. DialogResult is a property of the Form. It can accept a range of values. As soon as you type a space after the equals sign, you'll see a list with these values on it: As you can see, one of these values is DialogResult.OK. This indicates that you want to use this button as an OK button. When the button is clicked, VB.NET will return a result of OK for this button. Access the code for your Cancel button and add the following line: Me.DialogResult = DialogResult.Cancel For the Cancel button, we're just selecting DialogResult.Cancel from the list. When the button is clicked, VB.NET will return a result of Cancel for this button. You can test to see what value is stored in Me.DialogResult. But you do that from the button that displays the form, Form1 for us. So access your Form1 code, and locate the lines that display the second form. The two lines should be these: Dim frmDialogue As New frmSecond frmDialogue.ShowDialog() Change the second line to this: If frmDialogue.ShowDialog() = DialogResult.OK Then MsgBox("OK Button Clicked") End If To get at the value of the button clicked, you test to see what result the ShowDialog property is. If the ShowDialog property of frmDialogue is OK then you can execute the code that needs executing. If the Cancel button was clicked, however, you don't have to do anything: VB.NET will take of closing your Modal dialogue box for you! Run your programme and test it out. Click your button to bring up your Modal dialogue box. Click the OK button, and you should see the message box display. Bring the Modal dialogue box up a second time and then click the Cancel button. The form will just close down. In the next part, we'll see how to return values from a second. The form with OK and Cancel buttons on it is not doing much good. We need it do some work for us. Let's turn the form into a Change Case dialogue box. Design a Form like the one in the following image (this is frmSecond): When you've designed your form, click back on Form1 and add a Textbox to it. When the button on Form1 is clicked, the dialogue box above will display. You can then select an option button to change the case to Upper, Lower or Proper case. This will happen when the OK button is clicked. Whatever text is in Texbox1 on Form1 will be changed accordingly. Double click the OK button on frmSecond to access the code. You should have the following: Me.DialogResult = DialogResult.OK If you want to refer to Texbox1 on Form1, you can't just do this: Form1.Textbox1.Text In previous version of VB, that code would be all right. You're saying "Access the Text property of Textbox1 on Form1." The problem in VB.NET is that forms are Classes. They don't become objects until one is created from a Class. So the frmSecond Class knows nothing about Form1. It has no idea what it is. The solution is to create a textbox object variable on Form1, and assign Textbox1 to this variable. But this variable has to be something that all Classes in the project can see. So add this near the top of your code window for Form1 (add it just below the Inherits System.Windows.Forms.Form line, or Public Class Form1): Public Shared tb As TextBox We're setting up a variable which we've called tb. A Textbox object is going to be stored in this variable. But notice that the variable is Public Shared. This way, frmSecond will be able to see the variable. In the Form Load event for Form1, add the following line: tb = Textbox1 When Form1 loads, the textbox called Textbox1 will be assigned to the tb variable. Now Textbox1 can be seen by frmSecond. Go back to your code for the OK button on frmSecond. Add the following two lines at the top: Dim ChangeCase As String ChangeCase = Form1.tb.Text We're setting up a String variable called ChangeCase. Whatever text is in Textbox1 of Form1 will then be assigned to the ChangeCase variable. But notice that as soon as you type a full stop after Form1, the tb variable will be available in the pop up list: The Public variable called tb holds a reference to Textbox1 on Form1. When you type a full stop after the tb, you get a list popping up. The list is all the Properties and Methods that are available to Textbox1. One of these is the Text property. We now only need to add the code that does the actual converting. So add this below the two lines you already have: Dim ChangeCase As String ChangeCase = Form1.tb.Text If optUpper.Checked Then ChangeCase = ChangeCase.ToUpper ElseIf optLower.Checked Then ChangeCase = ChangeCase.ToLower ElseIf optProper.Checked Then ChangeCase = StrConv(ChangeCase, VbStrConv.ProperCase) End If Form1.tb.Text = ChangeCase The three options buttons on our form were called optUpper, optLower and optProper. In the code, we're using an If Statement to see which of these was selected. The one that was chosen will have its Checked property set to True. We then store into the variable ChangeCase the converted text from the textbox. The final line puts the converted text back into Textbox1 on Form1. But you're coding window should look like this: Note that the DialogResult.OK line is the final line of the code. When you're writing your code, make sure that optUpper, optLower and optProper are changed to whatever you called your Radio Buttons. When you're finished adding the code, run your programme. Enter some text into Textbox1. Then click the button that brings up the Change Case Dialogue box. Select an option from the three available, and the click OK. The text in Textbox1 should be converted. Setting and Getting value from one form to another can be quite a tricky process at first. But once you get the hang of it you'll find it's not too difficult. And that ends this section of this course. There's an awful lot more to learn about Windows Forms, and a bit of experimentation is needed before you become skilled in their use. But in a beginners course, you've learned enough to be going on with.