以前我有一个应用程序目标框架4.5.1，并使用Web引用添加一个WCF服务。这工作完美，并能够成功地与服务器进行身份验证。

旧代码：

ServicePointManager.Expect100Continue = false;
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

IService orderService = new Service();

// private method to load certificate
var cert = LoadCertificate(@"....\00050._.1.p12", "pwd");

oIPGApiOrderService.ClientCertificates.Add(cert);

oIPGApiOrderService.Url = @"service_url";

NetworkCredential nc = new NetworkCredential("username", "pwd");
oIPGApiOrderService.Credentials = nc;

现在我正在升级到.net核心2.0，目标是.net标准2.0。我已经添加了使用服务引用（连接服务）的服务。生成的代码已经改变，使用通道工厂等...

新代码：

ServicePointManager.Expect100Continue = false;
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

System.ServiceModel.BasicHttpBinding result = new System.ServiceModel.BasicHttpBinding();
result.MaxBufferSize = int.MaxValue;
result.ReaderQuotas = System.Xml.XmlDictionaryReaderQuotas.Max;
result.MaxReceivedMessageSize = int.MaxValue;
result.AllowCookies = true;
result.Security.Mode = System.ServiceModel.BasicHttpSecurityMode.Transport;

IService client = new Service(result, new EndpointAddress("service_url"));

client.ClientCredentials.ClientCertificate.Certificate = new X509Certificate2(@"....\00050._.1.p12", "pwd");

client.ClientCredentials.UserName.UserName = "username";
client.ClientCredentials.UserName.Password = "pwd";

但新代码不工作，虽然证书加载成功。我得到一个异常：

{System.ServiceModel.Security.SecurityNegotiationException: Could not establish trust relationship for the SSL/TLS secure channel with authority 'xxxxxxx-online.com'. ---> System.Net.Http.HttpRequestException: An error occurred while sending the request. ---> System.Net.Http.WinHttpException: A security error occurred

我很感激你们的帮助。我错过什么了吗？