public List<Book> GetBooks()
 {
     using (var db = new BooksContext())
     {
         var books = (from entity in db.Books
                      select entity).ToList();
         return books;
     }
 }
        public void AddBook(Book book)
        {
            using (var db = new BooksContext())
            {

                db.Books.Add(book);
                db.SaveChanges();

            }
        }