• Add a Button that says "Convert!"

Introduction to Visual Basic .NET

Launching VB

Select Start->Programs->Microsoft Visual Studio .NET 2003->Microsoft Visual Studio .NET.

When that loads, click on the New Project button. Select the Visual Basic folder and the Windows Application icon.

The Visual Studio will open up, which has buttons and lists all over the place. In the center will be a grey sub-window with black dots in it labeled "Form1". The tab "Form1.vb [Design]" above it will be selected (i.e. darker).

On the left is something that says "Toolkit". If you click on that, you'll see a list of GUI elements (what in this context are called controls.) You'll probably see Pointer, Label, Button, CheckBox, etc.

If you click on the little push-pin on the Toolkit window, it will hang. I don't know why. Instead, click on the X and then go to View->Toolbox. I think that will bring it up in an anchored window.

Pretty Pictures

Label1. Does that text suck, or what? Let's make it say something more interesting.

Go look in the bottom right-hand pane of Visual Studio. It should say Properties at the top of that little windowpane. (If it doesn't, select View->Properties Window and the Properties pane should appear somewhere.)

The Properties pane is mostly filled with a two-column table. Look for the left-hand cell that says Text. The right-hand side should say Label1; change that to say Lemurs rule!

Above the Text line are a bunch of lines having to do with the appearance of the text: font (which includes size and boldness and italicness), color, background color, alignment, font direction, etc. You can make it hot pink text on a cyan background. Go wild! Take a few minutes to have some fun with the text -- I can wait.

Code

Since MapQuest didn't convert miles to kilometers, let's make a quick tool to do that.

• Add a Label that says "Miles:".
• Add a TextBox
  • Change the (Name) property of the TextBox to MilesTextEntry.
  • Change the Text property to nothing (i.e. delete the characters "TextBox1").
• Add a Label that says "Kilometers:".
  • Change the (Name) property of the Label to KilometersTextOutput.
  • Change the Text property to "Kilometers:".
• Add a Buton that says "Convert!"
  • Change the (Name) property of the Button to ConvertButton.
  • Change the Text property to "Convert!".

Double click on Form1, and boom! suddenly you'll get a code window, with a cursor sitting inside a subroutine Form1_Load. That's the code that gets run when the form starts up. (You don't care about that right now.)

We don't care about doing something when Form1 is loaded, but you do want something to happen when you click on the Convert! button. So paste this in to the code:

    Private Sub ConvertButton_Click(ByVal sender As System.Object, 
                                    ByVal e As EventArgs) Handles ConvertButton.Click
        Dim miles As Double
        Dim km As Double
        miles = Val(MilesTextEntry.Text)
        km = miles / 0.6
        KilometersTextOutput.Text = "Kilometers: " + Str$(km)

    End Sub

Basically, the Foo_Click method is called when there is a click in the element named "Foo". In this case, it executes every time there is a click in ConvertButton.

All the junk about ByVal sender etc and e As EventArgs, etc? You don't need to worry about right now. Basically, it's passing around events in a way that isn't that different from how Java does it. You might need to use it once you start building prototypes for your project, but you might not. Learn it when you need it.

After the Private Sub line is some pretty basic miles-to-kilometers conversion math. Pretty simple.

Finally, you set KilometersTextOutput.Text to a new string, and the new string magically gets plopped in the right place in the windo and refreshed. It's magic, it does it all for you.

Running the code

• click on the little right-hand arrow (below and to the right of the Help menu item)
• OR Debug -> Start
• OR press F5

Error while trying to run project

If you do get "unable to start debugging" error message, all is not lost: go find your application on the file system. It's probably somewhere like My Documents -> Visual Studio Projects -> WindowsApplication1 -> obj -> Release -> WindowsApplication1. Click on file, and you should see a wonderful little window that says "Lemurs rule!" and has a miles to kilometers conversion tool.

Final notes

-- DuckySherwood - 25 Oct 2005