The Murky Future of ASP.NET AJAX
First a bit of history. Microsoft’s first attempt at an AJAX library started in late 2005 under the code name Atlas. In January of 2007 the first production version released as ASP.NET AJAX. In November of the same year, the library was promoted from a stand-alone offering to part of ASP.NET 3.5. A follow-up version was released with ASP.NET 4.0. Much of the functionality is centered around the UpdatePanel control, which will continue to be supported though it has lost favor among developers.
Released in parallel with ASP.NET AJAX was the Ajax Control Toolkit. Released on CodePlex, it continues to receive occasional bug fixes but they are few and far between. According to Dave Ward, much of its functionality is available in jQuery and jQuery UI, making its future uncertain.
Third up is the Microsoft Ajax Library, also known as the ASP.NET Ajax Library. Dave Ward says,
Though this library was stealthily “released” within the latest versions of the AJAX Control Toolkit distributions, it is deprecated, obsolete, is not supported by Microsoft in any form. It will receive no further development or bug fixes, and should not be used going forward.
He continues, “if you’re using a DataView or Sys.require, you’re using the now-obsolete ASP.NET Ajax Library and should consider a jQuery-based alternative.”