Using the For Loop

The For loop is probably the most popular of all Visual Basic loops. The Do loop doesn't need aloop index, but the For loop does; a loop index counts the number of loop iterations as the loop executes. Here's the syntax for the For loop—note that you can terminate a For loop at any time with Exit For:

For index = start To end [Step step]
    [statements]
    [Exit For]
    [statements]
Next [index]

The index variable is originally set to start automatically when the loop begins. Each time through the loop, index is incremented by step (step is set to a default of 1 if you don't specify a value) and when index equals end, the loop ends.

Here's how to put this loop to work; in this case, I'm displaying "Hello from Visual Basic" four times (that is, intLoopIndex will hold 0 the first time; 1, the next; followed by 2; and then 3, at which point the loop terminates):

Module Module1
    Sub Main()
        Dim intLoopIndex As Integer
        For intLoopIndex = 0 To 3
            System.Console.WriteLine("Hello from Visual Basic")
        Next intLoopIndex
    End Sub
End Module

Here's what you see when you run this code:

Hello from Visual Basic
Hello from Visual Basic
Hello from Visual Basic
Hello from Visual Basic
Press any key to continue

If I were to use a step size of 2:

For intLoopIndex = 0 To 3 Step 2
    System.Console.WriteLine("Hello from Visual Basic")
Next intLoopIndex

I'd see this result:

Hello from Visual Basic
Hello from Visual Basic
Press any key to continue

We'll see For loops throughout the book.