public ActionResult UpdateDeleteBook(Book book)
 {
     if (ModelState.IsValid)
     {
         if (Request.Form["delete"] == "yes") { ViewBag.Message = book.DeleteBook(book); }
         else { ViewBag.Message = book.UpdateBook(book); }
     }
     ViewBag.Results = book.AllBooks();
     return ViewIfAdminLoggedIn();
 }