When you want to use Code First feature in Visual Studio 11 or Entity Framework 4.1 then you might hit the error “‘DbContext’ could not be found”. If you are looking at the blog like http://blogs.msdn.com/b/adonet/archive/2011/03/15/ef-4-1-code-first-walkthrough.aspx you will wondering the EntityFramework cannot be found in Add Reference dialog box.
The EntityFramework is in fact a dll. You need to browse to the following location to get it.
c:\Program Files (x86)\Microsoft ASP.NET\ASP.NETMVC 4\Packages\EntityFramework 5.0.0-rc\lib\net45
You can use DbContext once you add the EntityFramework.dll. You need System.Data.Entity too.