Help me understand “LINQ to Entities only supports casting Entity Data Model primitive types”

Question

I have a unit of work and a repository using EF 4 and POCOs. Since EF requires an ordered set before it can Skip() and Take(), I added the following unit test (without mocks) j

Answer 1

It is spotting "order by {object}" and panicking; it knows how to order by string, int, short, DateTime, etc - but object is a bit too vague.

You're going to need the actual lambda to be typed correctly; the simplest approach would be to make Get generic, i.e.

.... Get<TIdentity>(
         Expression<Func<E, TIdentity>> orderbyLambda, int page, int pageSize)

and then:

orderbyLambda: p => p.ID

should (without you changing the code at the caller) automatically make that a Get<short>(...) in this case via generic type inference. The other option is to leave it as <E,object>, but re-write the expression tree at the receiver. More work.