A Visual Basic example of passing ByRef vrs. ByVal

Private Sub btnTesting_Click(ByVal sender As System.Object, _
                                                ByVal e As System.EventArgs) Handles btnTesting.Click

Dim intA As Integer
Dim intB As Integer

intA = 10
intB = 5

AddEmUp(intA, intB)

MsgBox(intA) ‘will print 10
MsgBox(intB) ‘will print 0

End Sub

Public Sub AddEmUp(ByVal intA As Integer, ByRef intB As Integer)

Dim intC As Integer

intC = intA + intB

MsgBox(intC) ‘will print 15

intA = 0
intB = 0

End Sub