if (url.StartsWith("https", StringComparison.OrdinalIgnoreCase))///https请求

            {

                ServicePointManager.Expect100Continue = true;

                ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls; //SSL3协议替换成TLS协议

                ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);

                webRequest = WebRequest.Create(url) as HttpWebRequest;

                webRequest.ProtocolVersion = HttpVersion.Version10;

            }

            else

            {

                webRequest = WebRequest.Create(url) as HttpWebRequest;

            }