public IHttpActionResult Create(AlbumModel albumModel)
        {
            if (!this.ModelState.IsValid)
            {
                return this.BadRequest(this.ModelState);
            }

            var newAlbum = new Album
            {
                Title = albumModel.Title,
                NumberOfSongs = albumModel.NumberOfSongs,
                Year = albumModel.Year,
            };

            this.data.Albums.Add(newAlbum);
            this.data.SaveChanges();

            albumModel.Id = newAlbum.Id;
            return this.Ok(albumModel);
        }
        public IHttpActionResult Update(int id, AlbumModel albumModel)
        {
            if (!this.ModelState.IsValid)
            {
                return this.BadRequest(this.ModelState);
            }

            var albumToUpdate = this.data.Albums.All().FirstOrDefault(a => a.Id == id);
            if (albumToUpdate == null)
            {
                return this.BadRequest("Such song does not exists!");
            }

            albumToUpdate.Title = albumModel.Title;
            albumToUpdate.Year = albumModel.Year;

            if (albumModel.NumberOfSongs != null)
            {
                albumToUpdate.NumberOfSongs = albumModel.NumberOfSongs;
            }
                      
            this.data.SaveChanges();

            var updatedAlbumModel = new
            {
                Id = albumToUpdate.Id,
                Title = albumToUpdate.Title,
                NumberOfSongs = albumToUpdate.NumberOfSongs,
                Year = albumToUpdate.Year
            };

            return this.Ok(updatedAlbumModel);
        }