public ActionResult Edit(Guid id)
        {
            var classroomRepository = new ClassroomRepository(_context);

            var classroom = classroomRepository.GetById(id);

            var courses = ReorderCourses(classroom);

            ViewBag.Courses = new SelectList(CourseViewModel.FromEntityList(courses, 0), "Id", "Name");

            var userRepository = new UserRepository(_context);

            ViewBag.Students = new SelectList(userRepository.ListActiveStudents(), "id", "Name");

            return(View(ClassroomViewModel.FromEntity(classroom)));
        }