public ActionResult Save(ServiceCenterViewModel serviceCenterViewModel)
        {
            var serviceCenter = serviceCenterViewModel.ServiceCenter;

            if(!ModelState.IsValid)
            {
                var centerViewModel = new ServiceCenterViewModel
                {
                    ServiceCenter = serviceCenter,
                    Cities = _context.Cities.ToList()
                };

                return View("ServiceCenterForm", centerViewModel);
            }

            if (serviceCenter.Id == 0)
                _context.ServiceCenters.Add(serviceCenter);
            else
            {
                var serviceCenterInDb = _context.ServiceCenters.SingleOrDefault(c => c.Id == serviceCenter.Id);
                serviceCenterInDb.CenterNumber = serviceCenter.CenterNumber;
                serviceCenterInDb.CityId = serviceCenter.CityId;
                serviceCenterInDb.Address = serviceCenter.Address;
                serviceCenterInDb.Phone = serviceCenter.Phone;
            }

            _context.SaveChanges();
            return RedirectToAction("Index");
        }
        public ActionResult New()
        {
            var centerViewModel = new ServiceCenterViewModel
            {
                ServiceCenter = new Models.ServiceCenter(),
                Cities = _context.Cities.ToList()
            };

            return View("ServiceCenterForm", centerViewModel);
        }
        public ActionResult Edit(int id)
        {
            var centerInDb = _context.ServiceCenters.Find(id);
            
            if (centerInDb == null)
                return HttpNotFound();

            var centerViewModel = new ServiceCenterViewModel
            {
                ServiceCenter = centerInDb,
                Cities = _context.Cities.ToList()
            };

            return View("ServiceCenterForm", centerViewModel);
        }