public IHistorySharp PopHistory()
 {
     if (CanGoback)
     {
         var hist = HistoryCollection[HistoryCollection.Count - 1];
         HistoryCollection.Remove(hist);
         RedoCollection.Add(hist);
         return(hist);
     }
     return(null);
 }
 private void DeleteItem(ClipboardDataItem item)
 {
     HistoryCollection.Remove(item);
 }