Code, Design and Applications
LOOP STRUCTURES
Loop structures allow you to execute one or more lines of code repetitively. You can repeat the statements until a condition istrue, until a condition is false, a specified number of times, or once for each object in a collection. The loop structures supported by Visual Basic include:
⦁ While
⦁ Do... Loop
WHILE
Sub CheckWhile()
Dim Counter As Integer = 0
Dim Number As Integer = 10
While Number > 6
Number = Number - 1
Counter = Counter + 1
End While
MsgBox("The loop ran " & Counter & " times.") ' Runs 4 times.
End Sub
To call the Procedure:
Call CheckWhile()
Sub ExitWhileExample()
Dim Counter As Integer = 0
Dim Number As Integer = 8
While Number <> 10
If Number < 0 Then
Exit While
Number = Number - 1
Counter = Counter + 1
End While
MsgBox("The loop ran " & Counter & " times.") ' Runs 9 times.
End Sub
To call the Procedure:
Call ExitWhileExample()
DO LOOP
Sub CheckWhileFirst()
Dim Counter As Integer = 0
Dim Number As Integer = 10
Do While Number > 6
Number = Number - 1
Counter = Counter + 1
MsgBox("The loop ran " & Counter & " times.") ' Runs 4 times.
End Sub
Sub CheckWhileLast()
Dim Counter As Integer = 0
Dim Number As Integer = 5
Do
Number = Number - 1
Counter = Counter + 1
Loop While Number > 6
MsgBox("The loop ran " & Counter & " times.") ' Runs 1 time.
End Sub
Sub ExitDoExample()
Dim Counter As Integer = 0
Dim Number As Integer = 8
Do Until Number = 10
If Number <= 0 Then Exit Do
Number = Number - 1
Counter = Counter + 1
Loop
MsgBox("The loop ran " & Counter & " times.") ' Runs 8 times.
End Sub