Round-trip Property on Entity Framework entity

Question

Hi,

I have a Candidate entity that is read/write to a Candidate table under EF 4.0. This all works great but I need to load another type of Candidate from our existing membership table via a stored proc and Function Import.

From the applications POV they are also a Candidate they just happen to have an additional attribute of Grade. I have added Grade to the Candidate entity and I can map my Function Import for loading a member. However, I then get a mapping error message from EF on compile that the Grade property doesn't exist on the Candidate table.

Now I don't want to add Grade to the candidate table I just want to load it onto the Candidate entity if we want to load a Member via the sproc. Can anyone recommend how to do this please?

I've tried inheritance but again I hit the problem of a fixed schema in the db. Perhaps I'm being too optimistic in my attempt to decouple the Model from the immovable object that is our DB?

Thanks in advance for any responses.