상속: ICommand
 public ProgressDialogWindowViewModel(
     ProgressDialogOptions options,
     CancellationToken cancellationToken,
     CancelCommand cancelCommand)
 {
     if (options == null) throw new ArgumentNullException("options");
     WindowTitle = options.WindowTitle;
     Label = options.Label;
     CancelCommand = cancelCommand; // can be null (not cancellable)
     cancellationToken.Register(OnCancelled);
     Progress = new Progress<string>(OnProgress);
 }
 public ProgressDialogWindowViewModel(
     ProgressDialogOptions options,
     CancellationToken cancellationToken,
     CancelCommand cancelCommand)
 {
     if (options == null)
     {
         throw new ArgumentNullException("options");
     }
     WindowTitle   = options.WindowTitle;
     Label         = options.Label;
     CancelCommand = cancelCommand; // can be null (not cancellable)
     cancellationToken.Register(OnCancelled);
     Progress = new Progress <string>(OnProgress);
 }