Friday, August 14, 2009

How to find the control that generated a postback

Had a little trouble finding a good example of how to identify the control that generated a postback within the page_load

There's a nice article for C#, after a bit of tinkering here's a VB implementation:

Public Function GetPostBackControl(ByVal curPage As Page) As Control

 Dim foundControl As Control
 Dim controlName As String = curPage.Request.Params.Get("__EVENTTARGET")

 If (Not controlName Is Nothing And controlName <> "") Then
  foundControl = curPage.FindControl(controlName)
  ' control causing postback must be a Button or imageButton
  For Each controlName In curPage.Request.Form.AllKeys

   ' image buttons have a ".x" or ".y" appended to name string
   If (controlName.EndsWith(".x") Or controlName.EndsWith(".y")) then
    controlName = controlName.Substring(0, controlName.Length - 2)
   End If

   Dim c As Control = curPage.FindControl(controlName)

   If (TypeOf c Is Button Or TypeOf c Is ImageButton) Then
    'first button we find is the one that caused the postback
    foundControl = c
    Exit For
   End If
 End If

 GetPostBackControl = foundControl

End Function

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