ASP.NET AJAX 1.0 shipped as a separate download that you
could install on top of ASP.NET 2.0. Starting with the .NET Framework 3.5
release, all of these features are built-in with ASP.NET, which means you no
longer have to download and install a separate ASP.NET AJAX setup when building
or deploying applications.
When you create a new ASP.NET application or web-site in VS
2008 that targets the .NET 3.5 Framework, VS will automatically add the
appropriate AJAX registrations in your web.config file and the core ASP.NET
AJAX server controls will show up in your toolbox.
The version of ASP.NET AJAX that ships with .NET 3.5 has a
number of nice improvements to it - including support for using
UpdatePanels with WebParts, support for WCF based JSON end-points, support for using the ASP.NET Profile, Role and Login Application Services using