public IActionResult AddAuthorToBook(long idAuthor, [FromBody] Author item) { if (item == null || item.authorid != idAuthor) { return(BadRequest()); } var author = authorRepository.FindByID(idAuthor); if (author == null) { return(NotFound("Could not find book with id : " + idAuthor + ". Please try again with valid id.")); } author.bookauthor = item.bookauthor; Author updatedBook = authorRepository.AddAuthorToBook(author); Console.WriteLine(" updatedBook = " + (updatedBook == null)); if (updatedBook.authorid == -1) { return(NotFound("Invalid author id : " + updatedBook.fname + ". Please try again")); } return(CreatedAtRoute("AddBook", new { idBook = idAuthor }, updatedBook)); }