解决Error"基础连接已经关闭: 未能为SSL/TLS 安全通道建立信任关系

WebResponse response = WebRequest.Create("https://……").GetResponse(); 

ServicePointManager.CertificatePolicy = new AcceptAllCertificatePolicy();  

internal class AcceptAllCertificatePolicy : ICertificatePolicy
    {
        public AcceptAllCertificatePolicy()
        {
        }

        public bool CheckValidationResult(ServicePoint sPoint,
           X509Certificate cert, WebRequest wRequest, int certProb)
        {
            // Always accept
            return true;
        }
    }

ServicePointManager.ServerCertificateValidationCallback = ValidateServerCertificate;

private bool ValidateServerCertificate(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
        {
            return true;
        }