Determine which UpdatePanel causes the partial (asynchronous) PostBack?

Question

In a page contains two UpdatePanels, How can I know which UpdatePanel causes the partial PostBack ?

I mean in the Page_L

Answer 1

In client side use:

function EndRequestHandler(sender, args) { if (Sys.WebForms.PageRequestManager.getInstance()._postBackSettings.asyncTarget == 'Id of element do postback') { // do something . . . } } Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequestHandler);