post 报文请求接口方法

        /// <summary>
        /// post 报文到接口服务器
        /// </summary>
        /// <param name="targetUri">路径</param>
        /// <param name="content">提交的报文</param>
        /// <returns>返回报文</returns>
        public static string PostData(string targetUri, string content)
        {
            HttpWebRequest httpRequest = null;
            HttpWebResponse hwr = null;
            System.IO.Stream requestStream = null;
            System.IO.Stream responseStream = null;

            try
            {
                Encoding encoding = Encoding.GetEncoding("utf-8");
                byte[] bytesToPost = encoding.GetBytes(content);

                string cookieheader = string.Empty;

                CookieContainer cookieCon = new CookieContainer();

                System.GC.Collect();  //垃圾回收
                System.Net.ServicePointManager.DefaultConnectionLimit = ;   //允许的最大并发数

                #region 创建HttpWebRequest对象
                httpRequest = (HttpWebRequest)WebRequest.Create(targetUri);
                #endregion

                #region 初始化HtppWebRequest对象

                httpRequest.CookieContainer = cookieCon;
                httpRequest.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.2; .NET CLR 1.1.4322; .NET CLR 2.0.50727)";
                httpRequest.ContentType = "application/x-www-form-urlencoded";
                httpRequest.Method = "POST";
                httpRequest.Headers.Add("Accept-Encoding", "gzip, deflate");

                if (cookieheader.Equals(string.Empty))
                {
                    cookieheader = httpRequest.CookieContainer.GetCookieHeader(new Uri(targetUri));
                }
                else
                {
                    httpRequest.CookieContainer.SetCookies(new Uri(targetUri), cookieheader);
                }
                #endregion

                #region 附加Post给服务器的数据到HttpWebRequest对象
                httpRequest.ContentLength = bytesToPost.Length;
                requestStream = httpRequest.GetRequestStream();
                requestStream.Write(bytesToPost, , bytesToPost.Length);
                requestStream.Close();
                #endregion

                #region 读取服务器返回信息

                hwr = (HttpWebResponse)httpRequest.GetResponse();
                string xzip = hwr.ContentEncoding;

                responseStream = hwr.GetResponseStream();
                string stringResponse = "";
                if (xzip == "gzip")
                {
                    //压缩，进行解压缩处理
                }
                else
                {
                    using (System.IO.StreamReader responseReader = new System.IO.StreamReader(responseStream, Encoding.UTF8))
                    {
                        stringResponse = responseReader.ReadToEnd();
                    }
                }

                #endregion

                return stringResponse;
            }
            catch (Exception ex)
            {
                return "";
            }
            finally
            {
                #region  关闭相应连接
                if (requestStream != null)
                {
                    requestStream.Close();
                    requestStream = null;
                }
                if (responseStream != null)
                {
                    responseStream.Close();
                    responseStream = null;
                }
                if (hwr != null)
                {
                    hwr.Close();
                    hwr = null;
                }
                if (httpRequest != null)
                {
                    httpRequest.Abort();
                    httpRequest = null;
                }
                #endregion
            }
        }