same here, included a reference to the dll and getting the following error: "'System.Collections.Generic.List<int>' does not contain a definition for 'Where' and no extension method 'Where' accepting a first argument of type 'System.Collections.Generic.List<int>' could be found (are you missing a using directive or an assembly reference?)".
Working with an aspx .Net 2.0 web-forms application in VS2012.