public async Task<IHttpActionResult> PutBook(int id, Book book)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

            if (id != book.Id)
            {
                return BadRequest();
            }

            db.Entry(book).State = EntityState.Modified;

            try
            {
                await db.SaveChangesAsync();
            }
            catch (DbUpdateConcurrencyException)
            {
                if (!BookExists(id))
                {
                    return NotFound();
                }
                else
                {
                    throw;
                }
            }

            return StatusCode(HttpStatusCode.NoContent);
        }
        public async Task<IHttpActionResult> PostBook(Book book)
        {
            if (!ModelState.IsValid)
            {
                return BadRequest(ModelState);
            }

            db.Books.Add(book);
            await db.SaveChangesAsync();

            //Load author name by accessing book with Entry(), finding the nav property
            //with Reference(), then loading it to the db with Load()
            db.Entry(book).Reference(x => x.Author).Load();

            var dto = new BookDTO()
            {
                ID = book.Id,
                Title = book.Title,
                AuthorName = book.Author.Name
            };


            return CreatedAtRoute("DefaultApi", new { id = book.Id }, dto);
        }