public ActionResult ListStudent(string classId)
        {
            RegisterModel registerModel = new RegisterModel();

            ViewBag.students = registerModel.GetStudentOfClass(classId);
            ClassModel classModel = new ClassModel();

            ViewBag.c = classModel.GetClass(classId);
            return(View());
        }
        public ActionResult AddMistake(string classId, int classNumber)
        {
            LessonModel lessonModel = new LessonModel();

            ViewBag.lesson = lessonModel.GetLesson(classId, classNumber);
            RegisterModel registerModel = new RegisterModel();

            ViewBag.students = registerModel.GetStudentOfClass(classId);
            TypeMistakeModel typeMistakeModel = new TypeMistakeModel();

            ViewBag.typeMistakes = typeMistakeModel.GetTypeMistakes();
            return(View());
        }