public async Task <IActionResult> Create(GradeDto gradeDto)
        {
            if (await _gradeService.GetGradeByNameAsync(gradeDto.GradeName.ToLower()) == false)
            {
                await _gradeService.AddAsync(_mapper.Map <Grade>(gradeDto));

                ViewBag.ErrorMessage = "";
                return(RedirectToAction("GetAll", "Grade"));
            }
            ViewBag.ErrorMessage = "Sistemde aynı isme ait sınıf bulunmaktadır...!";
            return(View(gradeDto));
        }