public ActionResult Create(Mail mail)
        {
            if (ModelState.IsValid)
            {
                db.Mails.Add(mail);
                db.SaveChanges();
                return RedirectToAction("Index");
            }

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