What Is Partial-Page Rendering?

Typically, web pages with the ASP.NET server controls perform a postback to the server when there is an action performed by the user on a control. The server renders all the controls into a page in response. It even renders the controls where its state has not been changed between postbacks. The new ASP.NET Ajax server controls render only a portion of the web page to enrich user experience and performance. Partial-page rendering is a concept of rendering only a portion of a web page to avoid complete page refreshes and improve the user experience. It can be achieved using Microsoft ASP.NET Ajax without writing any client scripts. It is actually made possible through the interaction of the server controls with the Microsoft Ajax Client Library. The page updates are taken care of automatically by the client code injected into the server controls.

The new server controls that ship with the ASP.NET Ajax server extensions framework include the UpdatePanel control, which is responsible for implementing the partial-page rendering behavior in your web applications. This new control helps in eliminating the page refresh during a postback just by writing a few lines of code and without any client script.