Use PageRequestManager To Trigger Javascript for Asynchronous Postback

In my last post Send Balk Data(Datatable) From Child Window To Parent
i explained how we can send bulk data from child window to parent. But if we are using Asp.Net ajax in client page i.e the postback is caused asynchronously, then we can't use the RegisterStartUpScript to call the javascript function. But instead we have to use the Microsoft's Ajax javascript framework. I did this with the use of PageRequestManager JS Class as follows

var postBackThroughAdd = false;
function addRequestManager()
{
var reqMgr=Sys.WebForms.PageRequestManager.getInstance();
reqMgr.add_beginRequest(
function()
{
//Do something before the call begins
}
)
reqMgr.add_endRequest(
function(sender,args)
{
if (args.get_error() == undefined)//Checks there is no error
{
if(postBackThroughAdd)
{
postBackThroughAdd = false;
addToQuote();
//Function to trigger the parent postback and flag set and close the page
}
}
}
)
}

Variable postBackThroughAdd is a flag variable, which is set "true" when the button for which we want to send the data to parent is clicked. The code is like

<asp:Button ID="btnAddPartNoToCatalog" runat="server" Text="Add" CssClass="formButton"OnCommand="btnAddPartNoToCatalog_Command" OnClientClick="postBackThroughAdd = true;" />

Here if any error occurs while setting the data in session through server event btnAddPartNoToCatalog_Command, i am simply throughing the error with some userfriendly message. The message will be shown in JS message box and args.get_error() will not be undefined. So the function addToquote() will not be called.
Note: addRequestManager() function should be called on bodyload so that the JS events are registered before they fires actully. With the help of PageRequestManager class you can do some other tasks like showing some message in div after some action has succeeded of failed, show/hide loading... div without using UpdateProgress but same functionality(In the beginRequest handler, set the div's "display" property to "block" and int endRequest hander display to "none").