Aggregating clients and client types
You should not need to populate the ClientTypes property with your own query. Usually it is handled by a navigation property that already knows how to handle related tables but for this to work you first need to set the foreign key properly. Since you did not post the models I cannot say if it would be possible in your case.

You can read this article explaining how it should work: Don’t use Linq’s Join. Navigate!

Then you should be able to load the relations with Include:

var x =
    from c in _context.Cases.Include("ClientTypes")
    where c.ClientID == code
    select c;


See also Loading Related Objects