12.1. jQuery or ASP.NET AJAX Framework?

There is certainly overlap in the functionality provided by jQuery and the ASP.NET AJAX Framework. Theoretically, there is nothing stopping you from using both (especially because now the ASP.NET AJAX Framework works very well with jQuery), but you don't want your users to have to download unnecessary additional scripts.

Each set of libraries has its own strength; the Microsoft Ajax libraries (discussed in Chapter 11) contain a rich data binding functionality and make it very easy to communicate with .NET web services and Ajax-enabled methods (as you will see, this is also possible with jQuery). In this release, Microsoft has done some work to integrate the two (see Chapter 11).

On the other hand, jQuery has arguably better support for manipulating and querying the DOM and is better supported with many examples and extensions or plug-ins.

My own preference is certainly jQuery over the Microsoft Ajax libraries for a general-purpose framework.