private void _peopleGrid_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            MyData d = Application.Current.Resources["appData"] as MyData;
            Person p = this._peopleGrid.SelectedItem as Person;
            var query = from c in d.Countries where c.Id == p.CountryId select c;
            Country found = query.FirstOrDefault();
            this._cityCombo.ItemsSource = found.Cities;
            // this._cityCombo.REFRESH????????????????
        }