Adding ASP.NET AJAX to an existing ASP.NET Application

To add ASP.NET AJAX features to an existing ASP.NET application:

1. Follow the instructions listed in this link (rather than copying and pasting from this on-line document, it's easier to open the web.config file located in the folder C:\Program Files\Microsoft ASP.NET\ASP.NET 2.0 AJAX Extensions\<version>\web.config instead):

   http://ajax.asp.net/docs/ConfiguringASPNETAJAX.aspx

2. Right-click your web project and select Add Reference from the shortcut menu. In the Add Reference dialog, select System.Web.Extensions then click OK.