The type 'System.Web.UI.ScriptManager' is ambiguous

[Shawn Smiley]

We just downloaded the Telerik ASP.net AJAX controls and are starting to integrate them into an existing, non-AJAX web application.  However something keeps inserting a reference to the old version 1.0 of the System.Web.Extensions library into the project which in turn causes us to get the following error:

The type 'System.Web.UI.ScriptManager' is ambiguous: it could come from assembly 'C:\WINDOWS\assembly\GAC_MSIL\System.Web.Extensions\3.5.0.0__31bf3856ad364e35\System.Web.Extensions.dll' or from assembly 'C:\WINDOWS\assembly\GAC_MSIL\System.Web.Extensions\1.0.61025.0__31bf3856ad364e35\System.Web.Extensions.dll'. Please specify the assembly explicitly in the type name.

Everything works fine for awhile if I edit the web.config file and remove the following line:
<add assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>

However that assembly reference line gets inserted again as soon as I edit any of the controls in the VS Design surface.

Can anyone point me at what may be causing Visual Studio 2005 to keep inserting that assembly reference?


Thank you.

[Shawn Smiley]

I think I solved my own problem.  It helps to fully read the documentation.

I missed the step on adding AJAX support to an existing application in the docs at http://www.telerik.com/help/aspnet-ajax/adding%20radcontrols%20prometheus%20to%20an%20existing%20application.html

I haven't experienced this problem again since following those instructions.