//classId
        public GradeBook Get(int id)
        {
            var gradeBook = new GradeBook();
            var _gradeBookRepository = new GradeBookRepository();
            var _teacherRepository = new TeacherRepository();
            var _rosterRepository = new RosterRepository();

            gradeBook.StudentsEnrolled = _rosterRepository.GetStudentsEnrolledIn(id);
            gradeBook.Course = _teacherRepository.GetCourseById(id);
            gradeBook.AssignmentList = _gradeBookRepository.GetListOfAssignmentsById(id);
            gradeBook.StudentPerformances = _gradeBookRepository.GetListOfStudentPerformanceById(gradeBook.StudentsEnrolled);
            return gradeBook;
        }