Entity Framework 4 - How work around to use cast with interfaces

Question

How can I use cast in Linq to Entities?

I need something like this:

if (typeof(myObject) is IMyInterface)
{
  return MyObjectSet.Where(x => ((IMyInterface)x).MyProperty == 1);
}

If I try above code, I get an exception. It's an expected behavior of EF or it's a bug?

Answer 1

Instead of casting, you might want to use the OfType extension method:

return MyObjectSet.OfType<IMyInterface>().Where(x => x.MyProperty == 1);

Answer 2

This is expected. Since your interface is not in your EDMX, the EF doesn't know how to map it in an L2E query. Hard to give a good workaround without really knowing what problem you're trying to solve.