Question: system.web.httpcontext' is defined in an assembly that is not referenced?
Answer: CS0012 C# The type 'HttpContext' is defined in an assembly that is not referenced. ... CS0012 C# The type 'HttpContext' is defined in an assembly that is not referenced. You must add a reference to assembly 'System. Web, Version=4.0. 0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.