Visual Basic .NET Language Looping For...Next
Example
For...Next loop is used for repeating the same action for a finite number of times. The statements inside the following loop will be executed 11 times. The first time, i will have the value 0, the second time it will have the value 1, the last time it will have the value 10.
For i As Integer = 0 To 10
'Execute the action
Console.Writeline(i.ToString)
Next
Any integer expression can be used to parameterize the loop. It is permitted, but not required, for the control variable (in this case i) to also be stated after the Next. It is permitted for the control variable to be declared in advance, rather than within the For statement.
Dim StartIndex As Integer = 3
Dim EndIndex As Integer = 7
Dim i As Integer
For i = StartIndex To EndIndex - 1
'Execute the action
Console.Writeline(i.ToString)
Next i
Being able to define the Start and End integers allows loops to be created that directly reference other objects, such as:
For i = 0 to DataGridView1.Rows.Count - 1
Console.Writeline(DataGridView1.Rows(i).Cells(0).Value.ToString)
Next
This would then loop through every row in DataGridView1 and perform the action of writing the value of Column 1 to the Console. (The -1 is because the first row of the counted rows would be 1, not 0)
It is also possible to define how the control variable must increment.
For i As Integer = 1 To 10 Step 2
Console.Writeline(i.ToString)
Next
This outputs:
1 3 5 7 9
It is also possible to decrement the control variable (count down).
For i As Integer = 10 To 1 Step -1
Console.Writeline(i.ToString)
Next
This outputs:
10 9 8 7 6 5 4 3 2 1
You should not attempt to use (read or update) the control variable outside the loop.
