public TrackData ReadTrackByReference(IModelReference id)
        {
            // get track collection
            var col = db.GetCollection <TrackDataDTO>("tracks");

            // return by id
            var result = col.FindById(new BsonValue(id.Id));

            return(TrackDataDTO.CopyToTrackData(result));
        }
        public TrackData ReadTrackByISRC(string isrc)
        {
            // get track collection
            var col = db.GetCollection <TrackDataDTO>("tracks");

            // return by isrc
            var result = col.FindOne(x => x.ISRC == isrc);

            return(TrackDataDTO.CopyToTrackData(result));
        }