Question

I Supplier class:

public class Supplier {
    ....
    ....
    ....
}

I have also Subcontractor class and Subcontractor is a Supplier:

public class Subcontractor:Supplier {
    ....
    ....
    ....
}

In my db I have Suppliers table with data and another table with id field which is act as foreign key to suppliers table and I have in there also the subcintractor data.

In the entity framework edmx file I declared the inheritance relation:

Now I want to gett all the suppliers which are not subcontractors so I am doing:

context.Suppliers.OfType<Supplier>();

But this returns also the subcontractors..

How can I get only the Suppliers that are not subcontractors?

Answer 1

Give this a try:

context.Suppliers.Where(s => !(s is Subcontractor));

Edit

If you have more than one class which derives from Supplier the only option with LINQ to Entities seems to be something like:

context.Suppliers.Where(s => !(s is Subcontractor) 
                          && !(s is DerivedClass2)
                          && !(s is DerivedClass3)); // etc.

Entity SQL supports an ONLY keyword which allows to query for a specific type. But a corresponding counterpart is not available as LINQ operator.

Here is an implementation of an OfTypeOnly<TEntity> operator but it makes heavy use of metadata information and manual expression building and might be overkill in simple scenarios.