public ActionResult Edit(City city)
        {
            if(ModelState.IsValid)
            {
                db.Entry(city).State = EntityState.Modified;
                db.SaveChanges();
                return RedirectToAction("Index");
            }

            return View(city);
        }
        public ActionResult Create(City city)
        {
            if(ModelState.IsValid)
            {
                db.Cities.Add(city);
                db.SaveChanges();
                return RedirectToAction("Index");
            }

            var cities = db.Cities.ToList();
            return View(cities);
        }