The ASP.NET AJAX Framework provides many mechanisms to embed rich-client functionality in ASP.NET applications.  This framework provides a client-side set of components that extend JavaScript by providing a series of components meant to aid integration and development of web services, control extenders, and more.  All of these objects fit within the patterns Microsoft set forth in regards to their approach of AJAX development.  In addition, the ASP.NET AJAX Framework contains a set of server-side components and base classes that you can leverage in your custom AJAX components.

I've heard people ask why it is needed.  After all, AJAX is regularly available without the need of a specialized framework.  But what this framework is attempting to do is make development of AJAX components easier and more managed.  They've include a client-side framework that mimics the ASP.NET framework, by including classes and class inheritance, interface definitions, type checking and reflection, and many other mechanisms used in ASP.NET.  We'll take a look at that in this article.