public class ICBCUtil
    {
        public static string CheckOrder(
            string apiUrl,
            string strOrderNum,
            string strTranDate,
            string strShopCode,
            string strShopAccount,
            out string errInfo)
        {
            errInfo = string.Empty;
            //string api_url = "https://工行接口服务器地址/servlet/ICBCINBSEBusinessServlet";
            string api_url = "https://corporbank.icbc.com.cn/servlet/ICBCINBSEBusinessServlet";
            string post_params = "APIName=EAPI&APIVersion=001.001.002.001&MerReqData=";
            string cert_path = HttpContext.Current.Server.MapPath("~\\bin\\ca.cer");
            string cert_password = "********";
            StringBuilder sb = new StringBuilder();
            sb.Append("<?xml  version=\"1.0\" encoding=\"GBK\" standalone=\"no\" ?><ICBCAPI><in><orderNum>");
            sb.Append(strOrderNum);
            sb.Append("</orderNum><tranDate>");
            sb.Append(strTranDate);
            sb.Append("</tranDate><ShopCode>");
            sb.Append(strShopCode);
            sb.Append("</ShopCode><ShopAccount>");
            sb.Append(strShopAccount);
            sb.Append("</ShopAccount></in></ICBCAPI>");

            string post_data = post_params + sb.ToString();

            //return PostDataBySSL(post_data, api_url, cert_path, cert_password, out errInfo);
            return PostDataBySSL(post_data, apiUrl, cert_path, cert_password, out errInfo);
        }

        private static string PostDataBySSL(
            string post_data,
            string url,
            string cert_path,
            string cert_password,
            out string errInfo)
        {
            errInfo = string.Empty;

            try
            {
                ASCIIEncoding encoding = new ASCIIEncoding();
                //Encoding encoding = Encoding.Default;
                byte[] data = encoding.GetBytes(post_data);
                if (cert_path != string.Empty)
                {
                    ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(ValidateServerCertificate);
                }

                WebRequest webRequest = WebRequest.Create(url);
                //HttpWebRequest httpRequest = webRequest as HttpWebRequest;

                if (cert_path.ToLower().EndsWith(".cer"))
                {
                    httpRequest.ClientCertificates.Add(X509Certificate.CreateFromCertFile(cert_path));
                }
                else
                {
                    httpRequest.ClientCertificates.Add(new X509Certificate2(cert_path, cert_password));
                }

                httpRequest.KeepAlive = true;
                httpRequest.UserAgent = "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; Trident/4.0)";
                httpRequest.ContentType = "application/x-www-form-urlencoded";
                httpRequest.Method = "POST";

                httpRequest.ContentLength = data.Length;
                Stream requestStream = httpRequest.GetRequestStream();
                requestStream.Write(data, 0, data.Length);
                requestStream.Close();

                Stream responseStream = null;

                responseStream = httpRequest.GetResponse().GetResponseStream();
                string stringResponse = string.Empty;
                if (responseStream != null)
                {
                    using (StreamReader responseReader = new StreamReader(responseStream, Encoding.GetEncoding("GBK")))
                    {
                        stringResponse = responseReader.ReadToEnd();
                    }
                    responseStream.Close();
                }
                return stringResponse;
            }
            catch (Exception e)
            {
                errInfo = e.Message;
                return string.Empty;
            }
        }

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

PostDataBySSL这个方法SSL连接有没有问题，执行后服务器返回有异常信息

远程服务器返回错误: (403) 已禁止。

不知道是不是证书问题，还是证书的权限不够，

请知道的大牛指点指点。