How To Perform Client Side Action After Completion Of AJAX Postback Operation[ASP.NET 2.0]

ASPX Page IconWhile developing an ASP.NET 2.0 web application that uses <asp:UpdatePanel> control, we were required to perform a client side action (using JavaScript) after completion of Ajaxed post back.

We achieved it by attaching an event handler method to the event _endRequest of PageRequestManager object. After completion of every post back ASP.NET automatically notifies all the event handlers attached to the event _endRequest.

Here is the sample JavaScript. The first method attaches an event handler to _endRequest event and the second method is the event handler that is responsible for displaying an alert message on completion  of every post back.

<script type="text/javascript">
//Add an event handler to listen to _endRequest events
function Register() 
//This method is invoked after completion of post back operation.
//In this method add all the client side script that needs 
//to be executed after the post back.
function EndRequestHandler(sender, args) 
  alert("Post back completed");

Here is the sample ASPX code to call the Register() method on page load and controls required to perform simple Ajax operation.

<body onload="Register();">
    <form id="form1" runat="server">
    <asp:ScriptManager ID="scriptmanager" runat="server" />
        <asp:UpdatePanel ID="upPanel" runat="server">
                <asp:Label ID="lblMessage" runat="server" />
                <br />
                <asp:Button ID="btnClick" runat="server" 
                  Text="Click Here" 
                  OnClick="btnClick_OnClick" />

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