Linq To Entities О группеJoin (LeftJoin)

Question

Table Student
id int primary key
name nchar(10)
class_id int FOREIGN KEY to class'id

Table Class
id int primary Key
name nchar(10)

Тестовая база на ядре .net 3, ядре платформы сущностей, sql 2012, исключение "NavigationExpandingExpressionVisitor".

var query = _context.TestClass.GroupJoin(_context.TestStudent,
    cla = > cla.Id,
    stu = > stu.ClassId, (cla, stuCollection) = > new {
        className = cla.Name,
        studentsNames = stuCollection.Select(s = > s.Name)
    }
);
foreach(var arr in query) {
    Console.WriteLine("Class {0} Has {1} Students", arr.className, arr.studentsNames.Count());
}