Here's the solution:
MyCustCustomerService.AxdEntity_CustTable _CustCustTable = custResp.CustTable.First();
foreach (var dirParty in _CustCustTable.DirParty[0].DirPartyPostalAddressView)
{
if (dirParty.Roles.Contains("Invoice"))
{
DealerAddrTextBox1.Text = dirParty.Street;
DealerCSZipTextBox.Text = dirParty.City + ", " + dirParty.State + " " + dirParty.ZipCode;
DealerCountry.Text = dirParty.CountryRegionId;
}
}