public CommandState GetCommandState(FindReferencesCommandArgs args)
        {
            var pos = args.TextView.Caret.Position.BufferPosition;

            if (NavigationService.CanFindReferences(args.SubjectBuffer, pos))
            {
                return(CommandState.Available);
            }

            // visible but disabled
            return(new CommandState(true, false, false, true));
        }