private void Host_PropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            if (e.PropertyName != "CurrentPresenter") return;

            if (_config.Host.CurrentPresenter == _previousPresenter)
                return;

            _previousPresenter = _config.Host.CurrentPresenter;

            if (_previousPresenter == null)
                _stateManager.Remove(_config.HistoryKey);
            else
            {
                _stateManager.InsertOrUpdate(_config.HistoryKey, _previousPresenter.GetHistoryValue());
                _stateManager.CommitChanges(_previousPresenter.DisplayName);

                UpdateTitle(_previousPresenter);
            }
        }