public EditDiscsDetailsViewModel(IFolderProvider folderProvider, IDiscsService discService, IArtistsService artistService, IGenresService genreService)
 {
     this.folderProvider = folderProvider ?? throw new ArgumentNullException(nameof(folderProvider));
     this.discService    = discService ?? throw new ArgumentNullException(nameof(discService));
     this.artistService  = artistService ?? throw new ArgumentNullException(nameof(artistService));
     this.genreService   = genreService ?? throw new ArgumentNullException(nameof(genreService));
     Discs = new ObservableCollection <DiscViewItem>();
 }
 public DeleteContentViewModel(IDiscsService discService, ISongsService songService)
 {
     this.discService = discService ?? throw new ArgumentNullException(nameof(discService));
     this.songService = songService ?? throw new ArgumentNullException(nameof(songService));
 }