Question

I have a base class called BaseEvent.
And, 3 classes derived from BaseEvent: Derived1, Derived2, Derived3

Suppose we have a following query:

Database.BaseEvents.Where(e => e.EventsCategories.Any(
        c => c.EventCategories== category.OID)).ToList();

How to do that this query return collection of derived objects, not BaseEvent?

Thanks.

UPDATE:

but type should be Film

Answer 1

Use the Cast method:

Database.BaseEvents.Where(e => e.EventsCategories.Any(
    c => c.EventCategories== category.OID)).Cast<DerivedType>().ToList();

Assuming that is, you’ve setup Linq2Sql so that it understands your EventCategories property is a discriminator.

Update:
A discriminator field tells Linq2Sql what type it should use based on the value of a field. If you do not setup such a field. Linq2Sql will always return the base type. A google query will get you a ton of good posts on how to do this.