VB.Net - Do Loop

It repeats the enclosed block of statements while a Boolean condition is True or until the condition becomes True. It could be terminated at any time with the Exit Do statement.

The syntax for this loop construct is:

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Do { While | Until } condition
    [ statements ]
    [ Continue Do ]
    [ statements ]
    [ Exit Do ]
    [ statements ]
Loop
-or-
Do
    [ statements ]
    [ Continue Do ]
    [ statements ]
    [ Exit Do ]
    [ statements ]
Loop { While | Until } condition

Flow Diagram:

Example:

Module loops
   Sub Main()
      ' local variable definition 
      Dim a As Integer = 10
      'do loop execution 
      Do
          Console.WriteLine("value of a: {0}", a)
          a = a + 1
      Loop While (a < 20)
      Console.ReadLine()
   End Sub
End Module

When the above code is compiled and executed, it produces following result:

value of a: 10
value of a: 11
value of a: 12
value of a: 13
value of a: 14
value of a: 15
value of a: 16
value of a: 17
value of a: 18
value of a: 19

The program would behave in same way, if you use an Until statement, instead of While:

Module loops
   Sub Main()
      ' local variable definition 
      Dim a As Integer = 10
      'do loop execution 
      Do
          Console.WriteLine("value of a: {0}", a)
          a = a + 1
      Loop Until (a = 20)
      Console.ReadLine()
   End Sub
End Module

When the above code is compiled and executed, it produces following result:

value of a: 10
value of a: 11
value of a: 12
value of a: 13
value of a: 14
value of a: 15
value of a: 16
value of a: 17
value of a: 18
value of a: 19