I am trying to make a WebForms project and ASP.NET MVC per this question. One of the things I\'ve done to make that happen is that I added a namespaces node to the WebForms
Add System.Web.Mvc
in the compilation section,
<compilation debug="true">
<assemblies>
<add assembly="System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>
<add assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
<add assembly="System.Web.Abstractions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
<add assembly="System.Web.Routing, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
<add assembly="System.Web.Mvc, Version=1.0.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>
</assemblies>
</compilation>
It's easier to start with an MVC project, and then start adding WebForms pages.
For your error, you will need to add references for the following assemblies:
There will be much more to add in the web.config to get MVC working correctly. To get it all, I'd suggest creating an MVC project, and merging the web.config files.