public IHttpActionResult Post(SongRequestModel model)
        {
            if (!this.ModelState.IsValid)
            {
                return this.BadRequest(this.ModelState);
            }

            var song = new Song
            {
                Title = model.Title,
                Year = model.Year
            };

            this.data.Songs.Add(song);
            this.data.Songs.SaveChanges();

            return this.Ok(song);
        }
        public IHttpActionResult Put(int id, SongRequestModel model)
        {
            if (!this.ModelState.IsValid)
            {
                return this.BadRequest(this.ModelState);
            }

            var song = this.data.Songs
                .All()
                .FirstOrDefault(s => s.Id == id);

            if (song == null)
            {
                return this.BadRequest("Song with id " + id + " does not exist!");
            }

            song.Title = model.Title;
            song.Year = model.Year;

            this.data.Songs.Update(song);
            this.data.Songs.SaveChanges();

            return this.Ok(model);
        }