public ActionResult Create(Student student)
        {
            try
            {
                StudentGateway studentGateway=new StudentGateway();
                studentGateway.Insert(student);

                return RedirectToAction("Index");
            }
            catch
            {
                return View();
            }
        }
        public ActionResult Edit(Student student)
        {
            try
            {
                StudentGateway studentGateway=new StudentGateway();
                studentGateway.Update(student);

                return RedirectToAction("Index");
            }
            catch
            {
                return View();
            }
        }
        public ActionResult Delete(Student student)
        {
            try
            {
               StudentGateway studentGateway=new StudentGateway();
                studentGateway.Delete(student.Id);

                return RedirectToAction("Index");
            }
            catch
            {
                return View();
            }
        }
 public ActionResult Delete(int id)
 {
     StudentGateway studentGateway=new StudentGateway();
     Student student = studentGateway.GetAllStudents.Single(st => st.Id == id);
     return View(student);
 }
 public ActionResult Index()
   {
     StudentGateway studentGateway = new StudentGateway();
     List<StudentViewModel> studentViewModels = studentGateway.GetAll.ToList();
     return View(studentViewModels);
 }