AJAX and the ASP.NET 2.0 Callback Framework

Interaction with a Web application can be initiated via a synchronous page postback or an out-of-band postback, known as a client callback, from the client to the server.  The default ASP.NET Web page model uses synchronous page postbacks, which are usually triggered on the client by submitting an html form.  During a page postback, the Web page and controls are recreated and a new version of the