Monday, May 5, 2008

Manually Wiring Up the AJAX UpdateProgress Control

A common feature of AJAX-enabled pages is to have an animated "Please Wait" image appear while the partial page update is occurring. With ASP.Net this is implemented very easily. Here's an example:

<asp:updateprogress id="UpdateProgress1" runat="server" visible="true" associatedupdatepanelid="UpdatePanel1"></asp:updateprogress></span>
<span > <progresstemplate></progresstemplate></span>
<span > <div class="progress">
<span > <img src="" alt="" /></span>
<span >

<span > Please Wait</span>
<span > </span></div></span>
<span > </span>
<span > </span>

<span > <asp:updatepanel id="UpdatePanel1" runat="server"></asp:updatepanel></span>
<span > <contenttemplate></contenttemplate></span>
<span > <%-- Content goes here --%></span>
<span > </span>
<span > </span>

That's all there's supposed to be to it. Refer the UpdateProgress control to the UpdatePanel and it's just supposed to work. My experience hasn't been quite so straightforward. The progress indicator would appear some of the time, but not every time. The reason for this I do not know but my work last week to correctly warn a user when they're leaving a page early taught me about the AJAX Javascript events "Initialize Request" and "End Request". Today I used them to improve the consistency of the Progress Indicator:

<script type="text/javascript">
function InitializeRequestHandler(sender, eventArgs)
document.getElementById('<%=UpdateProgress1.ClientID%>').style.display = 'block';

function EndRequestHandler(sender, eventArgs)
document.getElementById('<%=UpdateProgress1.ClientID%>').style.display = 'none';


After adding this code, everything now works beautifully. The Progress Indicator displays every time, not just some of the time!

1 comment:

  1. Great post!
    This really allows to put all update progress code in one place like Master page and also create more complex progress behavior then just appearing and disappearing of DIV. Thanks!