ByVal vs ByRef
ByRef means that the code will manipulate the value. ByVal will manipulate a copy of the value. It is that simple as that. Check or try the sample I just made:
<summary> This is a sample: show you the difference between byVal and ByRef </summary> <remarks>Check Technologies ltée 2012</remarks> Public Class Form1 Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load TextBox1.Text = 2 Button1.Text = "addByVal" Button2.Text = "addByRef" End Sub Private Function addByVal(ByVal x) As Integer x = x * 2 addByVal = x End Function Private Function addByRef(ByRef x) As Integer x = x * 2 addByRef = x End Function Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click Label1.Text = addByVal(TextBox1.Text) End Sub Private Sub Button2_Click(sender As System.Object, e As System.EventArgs) Handles Button2.Click Label1.Text = addByRef(TextBox1.Text) End Sub End Class |
This is what Visual Studio 2010 looks like, a form with 2 buttons, 1 label and 1 TextBox:
When you run the code Button1 call the function addByVal while the other button calls addByRef. Inside both function, they are identical. Only the way you send the variable in the argument changes.
For your information, if you don’t put anything (byVal or ByRef) by default, is ByVal..
There are exceptions over exceptions if you are dealing with Arrays, Collections and others objects. You better check to make sure. And what is true in one language isn’t true in another language.
I am surprised that MSDN haven’t put more information.
ByVal (Visual Basic) : that an argument is passed in such a way that the called procedure or property cannot change the value of a variable underlying the argument in the calling code
ByRef (Visual Basic) : Specifies that an argument is passed in such a way that the called procedure can change the value of a variable underlying the argument in the calling code.
