public string SetStudentToTeacher(int IdSchool, int IdTeacher, int IdStudent)
        {
            if (!_dal.IsExist(IdStudent))
            {
                return("This Student Is Not Exist ");
            }
            if (!_dalschool.IsExist(IdSchool))
            {
                return("This School Is Not Exist ");
            }
            if (!_dalteacher.IsExist(IdTeacher))
            {
                return("This Teacher Is Not Exist ");
            }
            var Student = _dal.GetStudent(IdStudent);
            var Teacher = _dalteacher.GetTeaher(IdTeacher);

            ClassSchool Class = new ClassSchool()
            {
                Student = Student,
                Teacher = Teacher
            };

            _dal.SetStudntToTeacher(Class, IdSchool);
            return("true");
        }