public async Task <string> GetSubRegionIsoIds(string sub_key) { string isoID; if (HasSubDivisionsIsoId) { var isoids = this.GetAllSubRegionIsoIds().ToArray(); var index = GetSubRegionsKeys().ToList().IndexOf(sub_key); isoID = isoids[index]; } else { isoID = await AddressData.GetSubDivisionIsoID(this.Key, sub_key); } return(isoID); }