// PUT api/Albums/5
        public HttpResponseMessage PutAlbum(int id, Album album)
        {
            if (!ModelState.IsValid)
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
            }

            var albumToUpdate = db.Albums.FirstOrDefault(a => a.AlbumId == id);

            if (albumToUpdate != null && album != null)
            {
                albumToUpdate.UpdateWith(album);
            }
            else
            {
                return Request.CreateResponse(HttpStatusCode.BadRequest);
            }

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

            try
            {
                db.SaveChanges();
            }
            catch (DbUpdateConcurrencyException ex)
            {
                return Request.CreateErrorResponse(HttpStatusCode.NotFound, ex);
            }

            return Request.CreateResponse(HttpStatusCode.OK);
        }
        public void UpdateWith(Album album)
        {
            if (!string.IsNullOrWhiteSpace(album.AlbumTitle))
            {
                this.AlbumTitle = album.AlbumTitle;
            }

            if (album.AlbumYear.HasValue)
            {
                this.AlbumYear = album.AlbumYear;
            }

            if (!string.IsNullOrWhiteSpace(album.Producer))
            {
                this.Producer = album.Producer;
            }
        }
        // POST api/Albums
        public HttpResponseMessage PostAlbum(string artistName, [FromBody]AlbumDto album)
        {
            if (string.IsNullOrWhiteSpace(artistName))
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
            }

            var artist = db.Artists.Include(a => a.Albums).SingleOrDefault(a => a.ArtistName == artistName);
            if (artist == null)
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
            }

            if (artist.Albums.Any(a => a.AlbumTitle == album.AlbumTitle))
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
            }

            if (ModelState.IsValid)
            {
                var newAlbum = new Album
                {
                    AlbumTitle = album.AlbumTitle,
                    AlbumYear = album.AlbumYear,
                    Producer = album.Producer
                };

                db.Albums.Add(newAlbum);
                artist.Albums.Add(newAlbum);
                db.SaveChanges();

                HttpResponseMessage response = Request.CreateResponse(HttpStatusCode.Created, newAlbum);
                response.Headers.Location = new Uri(Url.Link("DefaultApi", new { id = newAlbum.AlbumId }));
                return response;
            }
            else
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
            }
        }