创建并发送请求，带xml

private static string NcPost(string url, string postCont, int timeOut, bool sign)
        {
            Encoding encoding = Encoding.GetEncoding("gb2312");
            byte[] bytesToPost = encoding.GetBytes(postCont);
            string cookieheader = string.Empty;

            var cookieCon = new CookieContainer();

            #region 创建HttpWebRequest对象

            var httpRequest = (HttpWebRequest)WebRequest.Create(url);

            #endregion

            #region 初始化HtppWebRequest对象

            httpRequest.CookieContainer = cookieCon;
            httpRequest.UserAgent = "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; .NET CLR 2.0.50727; .NET CLR 3.0.04506.648; .NET CLR 3.5.21022)";
            httpRequest.ContentType = "application/x-www-form-urlencoded";
            httpRequest.Method = "POST";
            httpRequest.Timeout = timeOut * 1000;
            if (sign)
            {
                httpRequest.ContentType = "INFOSEC_SIGN/1.0";
                httpRequest.ContentLength = bytesToPost.Length;
            }


            if (cookieheader.Equals(string.Empty))
            {
                httpRequest.CookieContainer.GetCookieHeader(new Uri(url));
            }
            else
            {
                httpRequest.CookieContainer.SetCookies(new Uri(url), cookieheader);
            }

            #endregion

            string stringResponse = "";
            try
            {

                #region 附加Post给服务器的数据到HttpWebRequest对象

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

                #endregion


                #region 读取服务器返回信息


                Stream responseStream = httpRequest.GetResponse().GetResponseStream();

                if (responseStream != null)
                {
                    using (
                        var responseReader = new StreamReader(responseStream, Encoding.GetEncoding("gbk")))
                    {
                        stringResponse = responseReader.ReadToEnd();
                    }
                    responseStream.Close();
                }

                #endregion
            }
            catch (Exception ex)
            {
                stringResponse = ex.ToString();
            }
            return stringResponse;
        }