How to user Ajax UpdateProgress with Iframe in ASP.NET

I ame trying to show a UpdateProgress image with iframe. But it is not working. I am using this iframe to display several pages. My code is as following..

---

        <iframe 
            runat="server" id="Iframe2" height="565" width="100%"   scrolling="no" 
            style="overflow-x:hidden;" fram开发者_StackOverflow社区eborder="0" marginheight="0" marginwidth="0" 
            vspace="0" hspace="0">                
        </iframe>  

     <asp:HiddenField ID="hdfIndex" runat="server" />                         
     </ContentTemplate>
            <Triggers>
                 <asp:AsyncPostBackTrigger ControlID="ibtnPrevious" EventName="Click" />
                 <asp:AsyncPostBackTrigger ControlID="ibtnNext" EventName="Click" />
                 <asp:AsyncPostBackTrigger ControlID="ibtnPage1" EventName="Click" />
                 <asp:AsyncPostBackTrigger ControlID="ibtnPage2" EventName="Click" />
                 <asp:AsyncPostBackTrigger ControlID="ibtnPage3" EventName="Click" />
                 <asp:AsyncPostBackTrigger ControlID="ibtnPage4" EventName="Click" />
                 <asp:AsyncPostBackTrigger ControlID="ibtnPage5" EventName="Click" />
            </Triggers>

---

But when I use it without iframe then it works nicely.

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In my opinion the best way to do this with iframes is to point the iframe to an aspx page having only the responsibility to redirect:

<iframe runat="server" id="Iframe2" height="565" width="100%"   scrolling="no" 
            style="overflow-x:hidden;" frameborder="0" marginheight="0" marginwidth="0" 
            vspace="0" hspace="0" src="Waiting.aspx?page=WebPageTarget.aspx">                
        </iframe>

And, in the Wating.aspx.cs:

protected void Page_Load(object sender, EventArgs e)
{
  var s = Request.QueryString["page"];
  ClientScript.RegisterStartupScript(GetType(), "gotorealpage",
                                     "window.location=\"" + s + "\";", true);
}

Of course, in the Waiting.aspx you put your waiting image.