Question

When I do the query:

Users.OfType<Student>().Where(u => u.StudentClasses.Any(sc => sc.Class.TermId == 1 && sc.Class.SubFormId == 1))

I get nothing. But this query returns true:

StudentClasses.Any(sc => sc.Class.TermId == 1 && sc.Class.SubFormId == 1)

So basically this is the same as:

Users.OfType<Student>().Where(u => true)

Which returns all the students. So OfType<Student> works.

I’m 100% sure that there are students in these classes StudentClasses but for some reason I get back no student although the subquery returns true.

Student is inherited from User, but only Student has StudendClass. What would be wrong with this query?

I basically want students in a particular subform/term (all these properties are in a Class.

I’m using Table per heirachy. Model builder:

modelBuilder.Entity<User>()
            .Map<Teacher>(m => m.Requires("UserType").HasValue("Teach"))
            .Map<Student>(m => m.Requires("UserType").HasValue("Stu"))
            .Map<Staff>(m => m.Requires("UserType").HasValue("Staff"));

Edit:

This also returns nothing:

Users.OfType<Student>().Where(u => u.StudentClasses.Any(sc => true))

Answer 1

I’m 100% sure that there are students in these classes StudentClasses.

I am 99% sure there aren’t. (1% for the potential case you have discovered some serious EF bug.) If there are students in classes with Class.TermId == 1 and Class.SubFormId == 1 your query must return those students.

Your test query…

(context.)StudentClasses.Any(sc => sc.Class.TermId == 1 && sc.Class.SubFormId == 1)

…has nothing to do with your original query. It only says that there is at least one row in the StudentClasses table with Class.TermId == 1 and Class.SubFormId == 1.

It doesn’t prove that you have any student which is in this particular class (or in these particular classes if there is more than one class with Class.TermId == 1 and Class.SubFormId == 1). All your students could be in the other classes and your original query would correctly return no student as result. So, this is by no means identical with (context.)Users.OfType<Student>().Where(u => true).

If you are still 100% sure you should show the content of your tables in a small example to make the problem reproducable for us.