I started using the Update Panel control recently to verify that an email address entered on a registration form was not a duplicate. If the email address as a duplicate, I wanted to display a simply JavaScript alert to notify the user without resorting to hidden fields. After much searching I found the The PageRequestManager Class and was able to leverage endRequest Event.
By adding the following PageRequestManager calls to a JavaScript block you can tap into the Begin and End AsyncPostback events
<script type="text/javascript"> Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(BegRequest); Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequest); function BegRequest(sender, args) { // add client-side code here } function EndRequest(sender, args) { // add client-side code here } </script>
Also, using the RegisterStartupScript method of the ScriptManager class you can easily inject JavaScript onto a page in a manner that’s almost identical to Page.ClientScript.RegisterStartupScript() method. Here’s an example of the ScriptManager call to inject a JavaScript alert.
ScriptManager.RegisterStartupScript( upDependents, typeof( UpdatePanel ) ,Guid.NewGuid().ToString(), string.Format( "DisplayErrorMessage('{0}');" ,errorMessage ), true );
