public object Register(CourseStudent info)
 {
     try
     {
         ValidateCourse(info);
         ValidateStudent(info);
         ValidateScore(info);
         var model = info.Map();
         using (var dao = new CourseStudentDAO())
         {
             return(dao.Register(model));
         }
     }
     catch (Exception)
     {
         throw;
     }
 }