Question regarding Update panel and partial postback?

suppose i have many server side controls in my update panel. so how could i kn开发者_运维技巧ow from the client side that which server side control causes partial postback in update panel. please help me with sample code.

You should register a handler for the update panel client event.

 Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(onBeginRequest);
 function onBeginRequest(sender, args) {
    var elem = args.get_postBackElement();
 }

The elem is the control you need. More info MSDN