public async Task <ActionResult <IEnumerable <MusicResource> > > GetAllMusicsByArtistId(int artistId) { var artist = await _artistService.GetById(artistId); if (artist == null) { return(NotFound("No such an artist")); } var musics = await _musicService.GetByArtistId(artistId); if (musics == null) { return(NotFound()); } var musicsResource = _mapper.Map <IEnumerable <Music>, IEnumerable <MusicResource> >(musics); return(Ok(musicsResource)); }