Paypal SetExpressCheckout(快速结账) 10731错误,请有经验的人帮忙

环境:C#.NET + Paypal SOAP API 版本:72.0

由于Paypal卖家保护策略要求商家必须提供一个发货地址 以下为我的代码:

var expResponse = client.SetExpressCheckout(ref csh, new SetExpressCheckoutReq()

            {

                SetExpressCheckoutRequest = new SetExpressCheckoutRequestType()

                {

                    SetExpressCheckoutRequestDetails = new SetExpressCheckoutRequestDetailsType()

                    {

                        ReturnURL = returnurl,

                        CancelURL = cancelurl,

                        BuyerEmail = CustomerHandle.GetIdentityName(),

                        PaymentDetails = new PaymentDetailsType[]

                        {

                            new PaymentDetailsType()

                            {

                                OrderTotal=OrderToal,

                                PaymentDetailsItem=new PaymentDetailsItemType[]

                                {

                                    new PaymentDetailsItemType

                                    {

                                        Amount = OrderToal,

                                        Number = "",

                                        Quantity = "1",

                                        Name =string.Format("#{0}#",orderNum)

                                    }

                                },

                                PaymentAction=PaymentActionCodeType.Sale,

                                ShipToAddress=new AddressType

                                {

                                    Name=string.Format("{0} {1}",shippingaddr.FirstName,shippingaddr.LastName),

                                    Street1=shippingaddr.ADD1,

                                    Street2=shippingaddr.ADD2,

                                    CityName=shippingaddr.City,

                                    StateOrProvince=shippingaddr.State,

                                    PostalCode=shippingaddr.Postcode,

                                    //Country=countrycode,

                                    /*paypal文档中说Country是必要的*/

                                    Country=CountryCodeType.NL,

                                    CountryName="Netherlands",

                                    

                                    Phone=shippingaddr.Postcode

                                }

                            }

                        },

                        AllowNote = "0",

                        cppheaderimage = ConfigurationManager.AppSettings["LOGOURL"],

                        BrandName = ConfigurationManager.AppSettings["BrandName"],

                        NoShipping = "0",

                        /*此外设置为1总是返回错误,设置为0无错误*/

                        AddressOverride = "1",

                        ReqConfirmShipping = "0"

                    },

                    Version = API_VERSION

                }

            });

当AddressOverride(Paypal说明是调用传递的地址将覆盖客户paypal账户中的地址) 设置为1(覆盖)时,

Country(一个枚举类型)和CountryName(string类型) 无论传递什么

结果都会包含一个异常:

10731 Shipping Address Country Empty The field Shipping Address Country is required

但是AddressOverride设置为0时就不会出现这个错误,请问哪位大哥有碰到过的?
帮下忙