VB.Net, ByVal and ByRef

Hi,

indeed, as long as you don't try to do any assignment in your sub/func, byval and byref will behave the same.

Here is the explanation : as its name doesn't suggest, a byval parameter is passed by reference ! ByRef is equivalent to C#'s ref keyword.

Here is a code snippet that should help you in identifying the difference :


'in your sub Main()
Dim a as String() = new String(){"0"}
test(a)

'change to  byref & test it
public sub test(byval s as String())
     s = new String(){"1","2","3"}
end sub

HTH,

-S

Thank you.

I am not understand String()....but my example shows I got the same result when did assignment in the sub:

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim a(0) As Integer
        test(a)
        MessageBox.Show(a(0))   'return 1 for both ByRef and ByVal.
    End Sub

    Private Sub test(ByRef s() As Integer)
        s(0) = 1
    End Sub

byval creates a new pointer for the array , byref passes the same pointer, as you found, it makes little difference.

the differenct is when you have a single object, as I understand it, byval passes a clone of the object whereas byref passes the object pointer.

in practice even though there is little difference you should use byref when you pass the referance, no point creating a new pointer if you dont need to and it makes the code understandable: the array is passed as a referance, not as a value.