The type initializer for 'System.Data.Entity.Internal.AppConfig' threw an exception

Question

I\'m working with EF5 in a MVC 4 aspnet website. Locally, everything works just fine, but when I publish it to the IIS and try to enter, I get the error

Answer 1

I had this error today on a nested MVC application running as virtual folder in onother MVC application. In my case the InnerException was more informative than the main one. It was stating:

- The entry 'DbContextMain' has already been added. (C:\inetpub\...\web.config line x)

After fixing the duplicate connection strings in the nested apps everything worked fine.