ASP.NET AJAX in .NET 3.5 and VS 2008

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.