You retrieve the instance of the client PageRequestManager object active in the client page and check whether an asynchronous postback is going on. If so, you call the abortPostBack method to stop it.

Important

Canceling an ongoing update in this way is equivalent to closing the connection with the server. No results will ever be received, and no updates will ever occur on the page. However, canceling the update is a pure client operation and has no effect over what’s happening on the server. If the user started a destructive operation, the client-side Cancel button can do nothing to stop that operation on the server.

The Ins and Outs of Partial Rendering

Overall, partial rendering is only one possible way to approach Ajax. It preserves most of your current investments and is relatively cheap to implement. Partial rendering just adds Ajax capabilities to your pages. There’s no architectural new point in partial rendering. It’s a great technique to quickly update legacy applications, and it is an excellent choice when you lack the time, skills, or budget to move on and redesign the application. But in a good number of cases, an improved user interface and optimized rendering is all that your users demand. So partial rendering would fit in perfectly.

On the other hand, building true Ajax applications where some of the presentation logic lives on the client written in JavaScript is not trivial either, and it requires a well-done and powerful client framework, as well as a server-side API that can be easily invoked