public ActionResult Show(int bookId, string authorId)
{
int newAuthorId = int.Parse(authorId);
List <Book> allBooks = Book.GetAll();
Book thisBook = Book.Find(bookId);
List <Author> allAuthors = Author.GetAll();
Author thisAuthor = Author.Find(newAuthorId);
thisAuthor.AddAuthorToBook(thisBook);
return(View(thisBook));
}