protected override void Initialize()
        {
            Debug.Assert(_listener == null);

            var rdt = (IVsRunningDocumentTable)GetService(typeof(SVsRunningDocumentTable));
            _listener = new SaveListener(rdt);

            base.Initialize();
        }
        protected override void Dispose(bool disposing)
        {
            Debug.Assert(_listener != null);

            _listener.Dispose();
            _listener = null;

            base.Dispose(disposing);
        }