public IActionResult Update(UpdateteacherViewModel viewModel)
        {
            if (!ModelState.IsValid)
            {
                return(View(viewModel));
            }

            _repository.Update(viewModel);
            return(RedirectToAction("Index"));
        }
        public IActionResult Update(int?id)
        {
            if (id == null || id == 0)
            {
                return(BadRequest());
            }

            var teacher = _repository.GetTeacher((int)id);

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

            UpdateteacherViewModel teacherViewModel = _factory.UpdateViewModel(teacher);

            return(View(teacherViewModel));
        }