Parameters Are Passed by Value

By default, in VBScript and earlier versions of Visual Basic, parameters passed to subroutines and functions are passed by reference. In Visual Basic .NET, however, parameters are passed by value.

When a parameter is passed to a function by value, changes to the parameter within the function are not reflected outside the function. When a parameter is passed by value, on the other hand, any changes made to the parameter are retained outside the function.

You can still use the ByVal and ByRef keywords to specify whether a parameter is passed by value or by reference. For example, the following page illustrates how to explicitly pass a parameter to a subroutine by value and by reference:

 <Script runat="Server"> Sub AddByVal( ByVal intParam )   intParam += 1 End Sub Sub AddByRef( ByRef intParam )   intParam +=1 End Sub </Script> <% Dim intNum As Integer = 3 ' intNum still equals 3 after AddByVal AddByVal( intNum ) ' intNum now equals 4 after AddByRef AddByRef( intNum ) %>