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AJAX stands for “Asynchronous JavaScript and XML,” and it’s a sort of blanket term coined in 2005 to indicate rich, highly interactive, and responsive Web applications that do a lot of work on the client and place out-of-band calls to the server. An out-of-band call is a server request that results in a page update rather than a page replacement. The net effect is that an AJAX Web application tends to look like a classic desktop Microsoft Windows application and has advanced features such as drag-and-drop and asynchronous tasks, a strongly responsive and nonflickering user interface, and far less user frustration.<br><br>ASP.NET AJAX Extensions is a significant extension to the ASP.NET platform that makes AJAX-style functionalities possible and effective. ASP.NET AJAX Extensions is designed to be part of ASP.NET and, therefore, seamlessly integrate with the existing platform and application model.<br><br>Architecturally speaking, the ASP.NET AJAX framework is made of two distinct elements: a client script library and a set of server extensions. The client script library is entirely written in JavaScript and, therefore, works with any modern browser. Server extensions are fully integrated with ASP.NET server-based services and controls. As a result, developers can write rich Web pages using nearly the same approach they know from developing classic ASP.NET server-based pages.<br><br>Most ASP.NET AJAX developers are former ASP.NET developers and, as such, are familiar with the server-side development model based on controls. The server-centric programming model is the next big step in the evolution of the ASP.NET programming model. ASP.NET AJAX server controls are great, especially if you don’t feel confident enough to create AJAX client scripts manually.<br><br>This book provides an overview of the ASP.NET AJAX framework with numerous examples to familiarize you with a variety of techniques and tools.<br><br>AJAX is a real breakthrough for ASP.NET developers and professionals. It makes cross-browser programming a reality and enables desktop-like functionalities over the Web.<br><br>