public RotateBatchViewModel(PdfRotator rotator)
        {
            _rotator = rotator;
            _destination = "";
            _sources = new ObservableCollection<string>();
            _sources.CollectionChanged += (object s, NotifyCollectionChangedEventArgs e) => {
                OnPropertyChanged(nameof(Sources));
                OnPropertyChanged(nameof(IsValid));
            };

            OpenOnComplete = true;
        }
        public RotateSingleViewModel(PdfRotator rotator)
        {
            _rotater = rotator;

            OpenOnComplete = true;
        }