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Question

How can I defer loading UpdatePanel content until after the page renders?

Answer 1

A:

Try something like this (not tested).

Set the UpdateMode of the UpdatePanel to Conditional.

Add this to your <head> section:

<script type="text/javascript">

    window.onload = __doPostBack('UpdatePanel1', ''); // Replace UpdatePanel1 with the ID of your UpdatePanel

</script>

Marko 2010-10-07 00:53:03

Answer 2

+1 A:

I had to do something very similar recently, here's how i did it (right or wrong):

The trick is a "Hidden Async Postback Trigger".

<asp:UpdatePanel ID="upFacebookImage" runat="server">
   <ContentTemplate>
      <!-- Your updatepanel content -->
   </ContentTemplate>
   <Triggers>
      <asp:AsyncPostBackTrigger ControlID="hiddenAsyncTrigger" EventName="Click" />
   </Triggers>
</asp:UpdatePanel>
<asp:Button ID="hiddenAsyncTrigger" runat="server" Text="AsyncUpdate" style="display:none;" />

Then from JavaScript, whenever you want to trigger the async postback, you do this:

__doPostBack('<%= hiddenAsyncTrigger.ClientID %>', 'OnClick');

In my example, i needed to trigger an async postback from a particular JS event. But you could attach it to doc ready.

I seem to remember trying @Marko Ivanovski's way, but for some reason it didn't work. I think you need to specify a "postback-able" control (ie a button) to trigger the postback.

HTH.

RPM1984 2010-10-07 02:42:00

Bingo, this did the trick. Slight modification though, in that I used GetPostBackEventReference(btnTrigger, string.Empty); and then RegisterStartupScript().

Bryan 2010-10-07 19:11:29

Yep, if you want to fire a particular server-side event handler, then yes - you'll need to do that. In my case i just needed a postback to run Page_Load again. Glad it worked.

RPM1984 2010-10-07 21:12:40

One downside... it appears that an UpdateProgress control will not be triggered if you manually postback.

Bryan 2010-10-07 21:36:34

Interesting (didnt require one in my scenario). You don't really `need` an UpdateProgress control - just create a hidden placeholder with and show it when you fire the async postback. The UpdateProgress control (like many other Web Forms Server Controls) is all about convinience, but can be easily replaced.

RPM1984 2010-10-07 22:39:29

Answer 3

A:

What if there are multiple update panels and each needs to be updated asynchronously?

Paul 2010-10-26 17:52:43

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How can I defer loading UpdatePanel content until after the page renders?

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