Tip #1: Understanding Cryptic MVC Errors

Some who try to use the Entity Framework with MVC may encounter the following error:

If you can see it the error reads:
CS0012: The type 'System.Data.Objects.DataClasses.EntityObject' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Data.Entity, Version=3.5.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089

I spent a good deal of time trying to add this reference to the View. However, for some reason despite I had the assembly in my Reference folder in the Project, it was not in the web.config.  Add the following line to the web.config:

<add assembly="System.Data.Entity, Version=3.5.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/>

Once you add this and rebuild, the error should go away.