public IActionResult Details(int?id)
        {
            if (id == null)
            {
                return(NotFound());
            }

            GradeViewModel gradeViewModel = _classroomService.GetGradeById(id.Value);

            if (gradeViewModel == null)
            {
                return(NotFound());
            }

            gradeViewModel.Student = _classroomService.GetStudentById(gradeViewModel.StudentId);
            return(View(gradeViewModel));
        }