void uiCountry_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            int countryId = Convert.ToInt32(uiCountry.SelectedValue);

            if (countryId > 0 && this.ContactTypeId == (int)ContactType.Site)
            {
                DataServiceHelper.ListCityAsync(countryId, null, ListCityCompleted);
            }
        }