C# Post发送数据返回页面结果

 public string GetPage(string posturl, string postData)
         {
             Stream outstream = null;
             Stream instream = null;
             StreamReader sr = null;
             HttpWebResponse response = null;
             HttpWebRequest request = null;
             Encoding encoding = Encoding.UTF8;
             byte[] data = encoding.GetBytes(postData);
             // 准备请求...
             try
             {
                 // 设置参数
                 request = WebRequest.Create(posturl) as HttpWebRequest;
                 CookieContainer cookieContainer = new CookieContainer();
                 request.CookieContainer = cookieContainer;
                 request.AllowAutoRedirect = true;
                 request.Method = "POST";
                 request.ContentType = "application/x-www-form-urlencoded";
                 request.ContentLength = data.Length;
                 outstream = request.GetRequestStream();
                 outstream.Write(data, , data.Length);
                 outstream.Close();
                 //发送请求并获取相应回应数据
                 response = request.GetResponse() as HttpWebResponse;
                 //直到request.GetResponse()程序才开始向目标网页发送Post请求
                 instream = response.GetResponseStream();
                 sr = new StreamReader(instream, encoding);
                 //返回结果网页（html）代码
                 string content = sr.ReadToEnd();
                 string err = string.Empty;
                 Response.Write(content);
                 return content;
             }
             catch (Exception ex)
             {
                 string err = ex.Message;
                 return string.Empty;
             }
         }