X509Certificate2（certpath）-不支持给定的路径格式

Question

当我通过httpwebrequest发送SSL证书时，出现错误-不支持给定的路径格式。这是代码。

string cerpath = @"c:\sagar\cert.cer";
string url = @"C:\localhost\";

Httpwebrequest req = (Httpwebrequest)WebRequest.Create(url);

X509Cetificate2 cert = new X509Certificate2(cerPath);

//Raises error The given paths format is not supported

req.ClientCertificate.Add(cert);