I have an MVC4/Web API project, with an Entity Framework, Code First data model. When I try to create a new API Controller with read/write methods using a data context &
Found the problem. In my model, I had a property with a custom enum type, which was in my business project. In my service project, I had my data model project referenced but not the business project. So adding a reference to the model AND business project allowed me to add scaffold controllers fine.
Seems obvious I know, but the error message it gives you is so unhelpful!
Anyway, I hope this helps anyone having the same problem, and can't fix it using the other suggestions.