X509Certificate2-无法返回远程服务器。（502）错误的网关

Question

我正在使用httpwebrequest将ssl证书传递给客户端。我正在错误以下。这是代码。

string url = "htttps:\\localhost:1990\api";
string certpath = "C:\Sagar\certi.pfx";
Httpwebrequest req = (Httpwebrequest) WebRequest.Create(url);
X509Certificate2 cert = new X509Certificate2(certPath, password); 
req.ClientCertificate.Add(cert);
StreamWriter sr = new StreamWriter(req.GetRequestStream());

// this line raises exception "The remote server returned error: (502) bad Gateway."
sr.write(requestBody);