Michael Schwarz, a German MVP for ASP and ASP.NET, published his free Ajax.NET library some time ago. It offers Ajax functionality (data exchange 316ith the server, including serialization of many data types), client callbacks, and some advanced features. The source code for Ajax.NET was eventually released to the public (see http://weblogs.asp.net/mschwarz/archive/2005/08/11/422293.aspx) and development on the library stopped. However, the code has since been moved into the BorgWorX project (see http://www.borgworx.net). Schwarz went on to work on Ajax.NET Professional (http://www.ajaxpro.info), which is available under a closed-source license, but is still free. Ajax.NET and Ajax.NET Professional can both be used with ASP.NET 1.1 and 2.0.