VB.Net/Language Basics/ByRef

Array passed By Reference

<source lang="vbnet"> Imports System Public Class MainClass

   Shared Sub Main(ByVal args As String())
     Dim i As Integer
     " declare array references
     Dim secondArray As Integer()
     Dim secondArrayCopy As Integer()
     " allocate secondArray and copy its reference
     secondArray = New Integer() {1, 2, 3}
     secondArrayCopy = secondArray
     Console.WriteLine(vbCrLf & "Test passing array " & _
        "reference using ByRef.")
     Console.Write("Contents of secondArray before " & _
        "calling SecondDouble: ")
     " print contents of secondArray before procedure call
     For i = 0 To secondArray.GetUpperBound(0)
        Console.Write(secondArray(i) & " ")
     Next
     " pass secondArray using ByRef
     SecondDouble(secondArray)
     Console.Write(vbCrLf & "Contents of secondArray " & _
        "after calling SecondDouble: ")
     " print contents of secondArray after procedure call
     For i = 0 To secondArray.GetUpperBound(0)
        Console.Write(secondArray(i) & " ")
     Next
     " test whether the reference was changed by SecondDouble
     If secondArray Is secondArrayCopy Then
        Console.WriteLine(vbCrLf & "The references are " & _
           "equal.")
     Else
        Console.WriteLine(vbCrLf & "The references are " & _
           "not equal.")
     End If

   End Sub
  " procedure modifies elements of array and assigns
  " new reference (note ByRef)
  Shared Sub SecondDouble(ByRef array As Integer())
     Dim i As Integer
     " double contents of array
     For i = 0 To array.GetUpperBound(0)
        array(i) *= 2
     Next
     " create new reference, assign it to array
     array = New Integer() {11, 12, 13}
  End Sub " SecondDouble

End Class

      </source>

Modify Array Element By Reference

<source lang="vbnet"> Imports System Public Class MainClass

   Shared Sub Main(ByVal args As String())
     Dim array1 As Integer() = New Integer() {1, 2, 3, 4, 5}
     Dim i As Integer
     Console.WriteLine( "The values of the original array are:" & vbCrLf )
     " display original elements of array1
     For i = 0 To array1.GetUpperBound(0)
        Console.WriteLine(  "  " & array1(i) )
     Next
     " array element passed by reference
     ModifyElementByRef(array1(3))
     Console.WriteLine(  vbCrLf & "array1(3) after " & _
        "ModifyElementByRef: " & array1(3) )
   End Sub
  Shared Sub ModifyElementByRef(ByRef element As Integer)
     Console.WriteLine(  vbCrLf & "Value received in " & _
        "ModifyElementByRef: " & element )
     element *= 2
     Console.WriteLine(  vbCrLf & "Value calculated in " & _
        "ModifyElementByRef: " & element )
  End Sub " ModifyElementByRef

End Class

      </source>

Pass parameter By value or By Reference

<source lang="vbnet"> Imports System Imports System.Diagnostics Public Class MainClass

   Shared Sub DoubleItByVal(ByVal X As Single)
       X *= 2
   End Sub
   Shared Sub DoubleItByRef(ByRef X As Single)
       X *= 2
   End Sub
   Shared Sub Main()
       Dim value As Single
       value = 10
       DoubleItByVal(value)
       Console.WriteLine(value)
       value = 10
       DoubleItByRef(value)
       Console.WriteLine(value)
   End Sub

End Class

      </source>