基础连接已经关闭: 未能为 SSL/TLS 安全通道建立信任关系_基础链接已关闭,未能为ss l

webservice接口调用时，抛出异常：“基础连接已经关闭: 未能为 SSL/TLS 安全通道建立信任关系“

解决方案：接口调用前先设置证书回调、和安全协议

ServicePointManager.ServerCertificateValidationCallback = (sender, certificate, chain, sslPolicyErrors) => true;
            ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3 | SecurityProtocolType.SystemDefault | SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12 | SecurityProtocolType.Tls13;