Entity Framework - Filter LINQ by ICollection type using TPH

Question

I'm have a class, Main , that has an ICollection of various types ( SubA and SubB , parent class is Parent ). I need to write a LINQ query that filters based on these subtypes in EF using table-per-hierarchy. TPH doesn't allow querying the Type column directly, so I'm trying to figure out a workaround. I have a method on Parent to get the type string. LINQ doesn't support this, however.

How can I perform a LINQ query from Main to filter on the type of each child ( SubA and SubB ), as well as one additional property of the child?

This is the class method to get the type:

public virtual string ReturnType()
{
    return GetType().BaseType.Name;
}

This is the LINQ query I was attempting, but fails because ReturnType() isn't supported in LINQ.

// Main query defined elsewhere in function
query = query.Where(main => main.children.All(child =>
                   (child.ReturnType() == "MS" || child.ReturnType() == "TL") &&
                   child.StatusId != 4);

Answer 1

You can do something like this:

query = query.Where(m => m.StatusId != 4 && (m is SubA || m is SubB));

Or trickier with OfType :

var subQuery = query.Where(m => m.StatusId != 4);
query = subQuery.OfType<SubA>()
                .Cast<Main>()
                .Union(subQuery.OfType<SubB>().Cast<Main>());