public override Slide Previous()
 {
     Text slide = null;
     // Check that next verse exists
     if ((currentVerseIndex - 1) > 0)
     {
         // Decrement counter to previous verse
         currentVerseIndex--;
         // Create a text slide with the text of the verse.
         slide = new Text();
         slide.Content = Verses[currentVerseIndex].Text;
     }
     return slide;
 }
 public override Slide Next()
 {
     Text slide = null;
     // Check that next verse exists
     if (Verses.Count > (currentVerseIndex + 1))
     {
         // Increment counter to next verse
         currentVerseIndex++;
         // Create a text slide with the text of the verse.
         slide = new Text();
         slide.Content = Verses[currentVerseIndex].Text;
     }
     return slide;
 }