private void StopHighlighter() {
   if (_highlighter == null) return;
   _highlighter.Dispose();
   _highlighter = null;
   ClearHighlighting(); 
 }
 private void StartHighligter() {
   if (_highlighter != null)
     StopHighlighter();
   if (chkDisableHili.Checked) return; 
   if (!_parser.Language.CanParse()) return; 
   _highlighter = new RichTextBoxHighligter(txtSource, _language);
   _highlighter.Adapter.Activate();
 }