https调用出现【基础连接已经关闭: 未能为 SSL/TLS 安全通道建立信任关系】错误

 1 先加入命名空间：
 2 
 3 using System.Net.Security;
 4 using System.Security.Authentication;
 5 using System.Security.Cryptography.X509Certificates;
 6 
 7 再重载CheckValidationResult方法，返回true
 8 
 9 public bool CheckValidationResult(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors errors)
10     {  // 总是接受  
11         return true;
12     }
13 
14 然后在HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(url);前面加上如下一行代码：
15 ServicePointManager.ServerCertificateValidationCallback = new System.Net.Security.RemoteCertificateValidationCallback(CheckValidationResult);