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Repeaters and Lost Data After Postback (Viewstate) October 8, 2009

Posted by codinglifestyle in ASP.NET, CodeProject.
Tags: , ,

Test question: I have a form which binds data to a Repeater on PageLoad.  The Repeater’s ItemTemplate contains a TextBox and Checkbox.  On postback the data is lost.  What’s wrong?

You may have found this page if you have been googling the following:

  • repeater postback lost data
  • dynamic control postback viewstate
  • data lost on postback

The problem is the Repeater is a dynamic control.  If you are binding in the codebehind, which we typically are, you have to realize that the textbox and checkboxes do not existuntil you DataBind().  Keeping that in mind, we should ask ourselves what is the order of execution of ViewState.  I think we can start to formulate our answer to the question above by realizing where I DataBind() and create my controls in relation to the workings of ViewState is why our data is lost on postback.

So, the answer: PageLoad is the wrong place to bind a Repeater or setup a dynamic control.  It is too late.  ViewState has already tried to resync your controls but they weren’t created yet.

What about the answer you want?  Stop toying with me and tell me the answer I hear you say.  Try OnInit().  If you bind there you’re controls will exist in time for ViewState to operate normally.

protected override void OnInit(EventArgs e)

I would have also accepted Repeaters are the evil frogspawn of Satan and should never be used unless you find peeling off your fingernails with rusty pliers appealing.

ref: http://weblogs.asp.net/ngur/archive/2004/05/17/133340.aspx, http://aspnet.4guysfromrolla.com/articles/092904-1.aspx