ASP.NET 4.0 with Ajaxcontroltoolkit 1.0 and system.web.extensions 1.0

We are looking into upgrading our asp.net 2.0 app开发者_Python百科lication to run on the 4.0 framework. We currently use system.web.extensions 1.0 and AjaxControlToolkit 1.0.

We made modifications to the toolkit and so we haven't upgraded it since. When I upgrade our solution and dependent projects to 4.0 I get the "sys is not defined" error which tells me it is not loading the correct versions of the above files.

I've tried all of the web.config settings possible for forcing it to use the 1.0 versions but to no avail.

Is it even possible to use the 4.0 framework with the system.web.extensions and ajaxtoolkit 1.0 versions?

Some of the resources may have changed going into the 4.0 framework and so you may need to include the correct References into the solution.