EDM: Error 11011: Association End key property 'Id' is not mapped.

Problem: receiving this error when building a project that includes an EDM:

Error 11011: Association End key property 'Id' is not mapped.

Solution: open as plain xml the .edmx file, remove everything related to the entity causing the error, then open the model with the designer and "Update model from database..." After you build, you should not get this error anymore.