基础连接已经关闭: 未能为SSL/TLS 安全通道建立信任关系

         #region private static bool ValidateServerCertificate 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。"
        /// <summary>
        /// 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。"
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="certificate"></param>
        /// <param name="chain"></param>
        /// <param name="sslPolicyErrors"></param>
        /// <returns></returns>
        private static bool ValidateServerCertificate(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
        {
            return true;
        }
        #endregion
                 
        ..............................
        ..............................
        .............................
        ServicePointManager.ServerCertificateValidationCallback = ValidateServerCertificate;
        byte[] responseArray = webClient.UploadValues(url, postValues);

在请求之前加上

ServicePointManager.ServerCertificateValidationCallback = ValidateServerCertificate;