From scratch, I made a new solution with two projects: one was MVC 3 and the other a supporting EF 4.2 project. The whole thing builds successfully. From the MVC project I
First of all you should check your connection string must be in your Web.Config file in the ROOT! of your project after that check if there is another connection string or not if there is another connection string replace it with your connection string.... This solved my problem which was same as your's....