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Passing by Value and by Reference in VB.NET

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Almost every one of us knows about passing objects by Value and by Reference, it is perhaps one of the lesser cared about aspects in programming. But if left unnoticed, it can cause unexpected results in our applications. This code sample demonstrates how we can pass a value by Reference and by Value in .NET viz. VB.NET and C#.

Save this file as PassVal.vb

Imports System
Imports Microsoft.visualbasic

Class TestRef

  Sub Change(ByRef
i As String)
    i = "Changed"
  End Sub

  Sub DontChange(ByVal i As String)
    i = "Some Text"
  End Sub

End Class

Class PassValue

  Shared Sub main()
    Dim objT As New
TestRef()
    Dim sChange As String = "DotNetExtreme"
    Dim sDontChange As
String = "DotNetExtreme"

    'Value of sChange will change 
    MsgBox("Before = " & sChange)
    objT.Change(sChange)
    MsgBox("After = " & sChange)

    'Value of sDontChange will not change 
    MsgBox("Before = " & sDontChange)
    objT.DontChange(sDontChange)
    MsgBox("After = " & sDontChange)
 
  End Sub
End Class

Compile the file from the command prompt as VBC Passval.vb.


Source: DotNetExtreme.com

This was first published in October 2003

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