How to use FOR NEXT loop in vb.net

Whenever you face a situation in programming to repeat a task for several times (more than one times ) or you have to repeat a task till you reach a condtition, in these situations you can use loop statements to achieve your desired results.

FOR NEXT Loop, FOR EACH Loop , WHILE Loop and DO WHILE Loop are the Commonly used loops in Visual Basic.NET 2005 ( VB.NET 2005) .

FOR NEXT Loop :

The FOR NEXT Loop , execute the loop body (the source code within For ..Next code block) to a fixed number of times.

  
For var=[startValue] To [endValue] [Step]
   [loopBody]
Next [var]

var : The counter for the loop to repeat the steps.

starValue : The starting value assign to counter variable .

endValue : When the counter variable reach end value the Loop will stop .

loopBody : The source code between loop body

Lets take a simple real time example , If you want to show a messagebox 5 times and each time you want to see how many times the message box shows.

  
1.	startVal=1
2.	endVal = 5
3.	For var = startVal To endVal
4.	    show message
5.	Next var

Line 1: Loop starts value from 1

Line 2: Loop will end when it reach 5

Line 3: Assign the starting value to var and inform to stop when the var reach endVal

Line 4: Execute the loop body

Line 5: Taking next step , if the counter not reach the endVal

VB.NET Source Code

  
Public Class Form1
    Private Sub Button1_Click(ByVal sender As System.Object,
	ByVal e As System.EventArgs) Handles Button1.Click
        Dim var As Integer
        Dim startVal As Integer
        Dim endVal As Integer
        startVal = 1
        endVal = 5
        For var = startVal To endVal
            MsgBox("Message Box Shows " &   var &   " Times ")
        Next var
    End Sub
End Class

When you execute this program , It will show messagebox five time and each time it shows the counter value.

If you want to Exit from FOR NEXT Loop even before completing the loop Visual Basic.NET provides a keyword Exit to use within the loop body.

  
For var=startValue To endValue [Step]
   [loopBody]
   Contition
   [Exit For]
Next [var]

Public Class Form1
    Private Sub Button1_Click(ByVal sender As System.Object, 
	ByVal e As System.EventArgs) Handles Button1.Click
        Dim var As Integer
        Dim startVal As Integer
        Dim endVal As Integer
        startVal = 1
        endVal = 5
        For var = startVal To endVal
            MsgBox("Message Box Shows "  var   " Times ")
            If var = 3 Then
                Exit For
            End If
        Next var
    End Sub
End Class