/// <summary>
 /// Loads the first file found after the current one and displays the first image if possible.
 /// </summary>
 private void NextFile()
 {
     if (_comicBook != null)
     {
         if (_comicBook.NextFile() == null)
         {
             FileNextPrevious fileNextPrevious = new FileNextPrevious();
             string file = fileNextPrevious.GetNextFileInDirectory(_comicBook.CurrentFile.Location);
             if (!string.IsNullOrEmpty(file))
             {
                 LoadAndDisplayComic(new string[] { file });
             }
         }
         else
         {
             byte[] image = _comicBook.CurrentFile.CurrentPage;
             if (image != null)
             {
                 DisplayImage(image, ImageStartPosition.Top);
             }
         }
     }
 }
 /// <summary>
 /// Show the previous file.
 /// </summary>
 private void PreviousFile()
 {
     if (_comicBook == null) { return; }
     if (_comicBook.PreviousFile() == null)
     {
         var fileNextPrevious = new FileNextPrevious();
         string file = fileNextPrevious.GetPreviousFileInDirectory(_comicBook.CurrentFile.Location);
         if (!string.IsNullOrEmpty(file))
         {
             LoadAndDisplayComic(new[] { file });
         }
     }
     else
     {
         byte[] image = _comicBook.CurrentFile.CurrentPage;
         if (image != null)
         {
             DisplayImage(image, ImageStartPosition.Bottom);
         }
     }
 }