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