Sub Procedures and Functions in Visual Basic .Net

Here we are discussing the sub procedure and functions in Visual Basic .Net.

Sub Procedure in Visual Basic .Net

A complete instruction with a meaning is called a statement in Visual Basic .Net. In VB.Net, a group of statements which together performs a task when it is called is known as a procedure. Similarly, a sub procedure in VB.Net is a group statements enclosed by the Sub and End Sub statements.

Sub Procedures returns control to the calling code after performing the task. Sub procedure do not return a value to the calling code. Every Visual Basic program must consist of a sub procedure called Main. Every programs in VB starts within the main procedure and end within the main().

Programmer can create new sub procedures in programs which should be called within the main procedure to work.

Example Program

Module Module1

   Sub main ( )
            custom_sub_procedure ( )
   End Sub

   custom_sub_procedure ( )
            console.WriteLine("Example Text")
   End Sub

End Module

In the above example, the programs starts and ends within the main ( ) procedure, the custom_sub_procedure ( ) will be called within the main sub procedure. Here, after executing the custom sub procedure, the control is transferred back to the main sub procedure.

The programmer can pass data through the parenthesis of sub procedures, these data are called arguments.

Example Program

Module Module1

     Sub Main ( )
        ----
     End Sub

     Sub diaply_msg (ByVal strText As String)
        ----
     End Sub

End Module

There are two types of argument passing they described below.

ByVal : Here the arguments passed by value. Which means the actual variable does not passes, but a copy of the variable is passed through the parenthesis. Any changes made to the variable does not affect the actual variable.

ByRef : In this case, the argument will be passed by reference. Here the location of the actual variable is passed, which means there is a direct access to the variable and so, any changes that made to the variable will be permanent.

Functions in Visual Basic .Net

In Visual Basic .Net, any sub procedure which returns a value to the calling code is known as a function. The functions are used in VB using a keyword Function.

Every functions in Visual Basic .Net are sub procedure where as every sub procedures are not functions.

Syntax

[modifier] Function function_name ( [parameter list]) As return type

         [statements]

End Function

Example

Public Function Sum (int a, int b) As integer

       s = a + b
       return s

End Function

Example Program

Module Module1

     Sub Main()

        Dim a As Integer = 5
        Dim b As Integer = 10
        Dim max As Integer = Findmax(a,b)

     End Sub

     Function Findmax(ByVal num1 As Integer, ByVal num2 As Integer) As Integer
        Dim Result As Integer
        If (num1>num2) Then
          Result = num1
        Else
          Result = num2
        End If
        Return Result 'returning the result value
     End Function

End Module

There are two methods to return a value from the function.

  • By using the return statement.
  • By assigning the value to the function name.

In the above example we used the first method, and if we use the second methods the statement Return Result is replaced with FindMax = Result.

Recursive Function

A recursive Function is one that calls itself.

Example Program

Module Module1
  Function factorial(ByVal num As Integer)
    Dim result As Integer
    If num = 1 Then
      Return 1
    Else
      result = factorial(num - 1) * num
      Return result
    End If
  End Function
 
  Sub Main()
    Console.WriteLine("Factorial = {0} ", factorial(6))
    Console.ReadKey()
  End Sub

End Module

 

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