private void BackButton_Click(object sender, RoutedEventArgs e)
 {
     if (FilesSelected != null)
     {
         FilesSelected.Invoke(this, null);
     }
 }
        private void NextButton_Click(object sender, RoutedEventArgs e)
        {
            if (FilesListBox.SelectedItems == null || FilesListBox.SelectedItems.Count == 0)
            {
                return;
            }

            if (FilesSelected != null)
            {
                var results = new ObservableCollection <string>();
                foreach (var item in FilesListBox.SelectedItems)
                {
                    results.Add(((FileEntry)item).File);
                }

                FilesSelected.Invoke(this, results);
            }
        }