c# 后台AJAX

public class BackA
    {
        #region 后台 AJAX
        public static string GetPage(string posturl)
        {
            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";//post的形式
                request.ContentType = "application/x-www-form-urlencoded";
                //request.ContentLength = data.Length;
                outstream = request.GetRequestStream();
                //outstream.Write(data, 0, 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;
                return content;
            }
            catch (Exception ex)
            {
                string err = ex.Message;
                //Response.Write(err);
                //return string.Empty;
                return err;
            }
        }
        #endregion
    }