MsgBox is not displaying the right value

I have a DropDownList, and when SelectedIndex is changed any event is triggered.

I'm putting on it for exemple msgbox, but it's not working.

What's the problem ?

EDIT;

now that's working after doing AutoPostBack = True. I did this, but i't giving me always '0' as开发者_运维百科 result

Protected Sub VD_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs)
MsgBox VD.SelectedIndex
End Sub

You need to have AutoPostBack = True and hook up an event to OnSelectedIndexChanged.

Have you set the AutoPostBack value on your control to true ?