Microsoft's ASP.NET AJAX Framework helps page developers design more interactive web pages by streamlining the postback mechanism. In traditional web pages, a full postback involves the browser re-requesting the page, which is then re-rendered. This re-rendered page markup is returned, in its entirety, to the browser for display. Ajax techniques improve the user's experience in two primary ways through the use of partial postbacks: first, a partial postback is asynchronous, meaning that the user can still interact with the page while waiting for the partial postback to complete; second, and more importantly, because a partial page postback updates only a particular region (or regions) of a page, less data needs to be shuttled between the client and the server, resulting in a quicker and smoother experience.

One benefit of full page postbacks is that the browser provides a number of cues to the user that a postback is underway. Upon the initiation of a postback, the little Internet icon in the browser's upper right corner starts spinning and a progress indicator is shown in the status bar, among other signs. With a partial page postback, however, no feedback is provided to the user. Consequently, a user may have instigated a partial page postback, but not realize it if the response is lagging. This may prompt them to click the button (or whatever instigated the partial postback) again, or they may just decry your website as buggy and close their browser, never to return again!

The good news is that the ASP.NET AJAX Framework includes the UpdateProgress control, a Web control designed specifically for providing visual feedback to a user during a long-running partial page postback. This article examines using the UpdateProgress. Read on to learn more!
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