public void MoveDown()
 {
     if (SourceList != null && SelectedItem != null)
     {
         var index = SourceList.IndexOf(SelectedItem);
         if (index != SourceList.Count - 1)
         {
             SourceList.Move(index, index + 1);
         }
     }
 }
 public void MoveUp()
 {
     if (SourceList != null && SelectedItem != null)
     {
         var index = SourceList.IndexOf(SelectedItem);
         if (index != 0)
         {
             SourceList.Move(index, index - 1);
         }
     }
 }