public ActionResult Create(School school)
        {
            //判斷Model驗證結果
            if (ModelState.IsValid)//若驗證成功,存入DB
            {
                ctx.School.Add(school);
                ctx.SaveChanges();
                return RedirectToAction("Index");//不能用return View("Index");
            }

            return View(school);//若View驗證失敗,顯示之前輸入的結果
        }
        public ActionResult Edit(School school)
        {
            if (ModelState.IsValid)
            {
                ctx.Entry(school).State = EntityState.Modified;
                ctx.SaveChanges();
                return RedirectToAction("Index");
            }

            return View(school);
        }