public IHttpActionResult Post(Book book)
        {
            book.Id = _books.Last() != null ? _books.Last().Id + 1 : 1;
            _books.Add(book);
            _booksBrodacaster.Value.BookAdded(book);

            return CreatedAtRoute("GetBookById", new { id = book.Id }, book);
        }
 public void BookAdded(Book book)
 {
     _booksHubContext.Clients.All.bookAdded(book);
 }