How to query the context so it creates subclassed POCO entities?
===

Say I have the following generated Entity Framework POCO class:

    public partial class Foo
    {
        #region Primitive Properties

        public virtual long Id { get; set; }

        #endregion
    }

And I subclass it:

    public class SubclassedFoo : Foo
    {
        public override long Id
        {
            get { return base.Id; }
            set { base.Id = value; }
        }
    }

How can the ObjectContext retrieve `SubclassedFoo` objects rather than `Foo` objects?

For example, what can I use instead of this?

    ObservableCollection<Foo> foos = context.Foos

as in:

    ObservableCollection<SubclassedFoo> subclassedFoos = context.???