public ActionResult Create(Tweet tweet)
        {
            if (ModelState.IsValid)
            {
                db.Tweets.Add(tweet);
                db.SaveChanges();
                return RedirectToAction("Index");
            }

            ViewBag.AuthorId = new SelectList(db.Users, "Id", "UserName", tweet.AuthorId);
            return View(tweet);
        }
 public ActionResult Edit(Tweet tweet)
 {
     if (ModelState.IsValid)
     {
         db.Entry(tweet).State = EntityState.Modified;
         db.SaveChanges();
         return RedirectToAction("Index");
     }
     ViewBag.AuthorId = new SelectList(db.Users, "Id", "UserName", tweet.AuthorId);
     return View(tweet);
 }