public ActionResult Create(ClassRoom classroom)
        {
            if (ModelState.IsValid)
            {
                db.Classs.Add(classroom);
                db.SaveChanges();
                return RedirectToAction("Index");
            }

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