public override void CanClose(Action<bool> callback)
        {
            if (IsDirty) {
                var dialog = new DialogViewModel("Are you sure you want to close?");
                windowManager.ShowDialog(dialog);

                callback(!dialog.IsCancelled);
            }
            else {
                callback(true);
            }
        }
        public override void CanClose(Action <bool> callback)
        {
            if (IsDirty)
            {
                var dialog = new DialogViewModel("Are you sure you want to close?");
                windowManager.ShowDialog(dialog);

                callback(!dialog.IsCancelled);
            }
            else
            {
                callback(true);
            }
        }