public ActionResult Create(Book book)
        {
            if (ModelState.IsValid)
            {
                db.Books.Add(book);
                db.SaveChanges();
                return RedirectToAction("Index");
            }

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