ashx获取另一个页面的返回内容

ashx获取另一个页面的值：
注：因为这是web请求，所以要http://...web路径
using System;
using System.Web;
using System.Web.SessionState;
using System.IO;
using System.Net;
using System.Text;



public void ProcessRequest(HttpContext context)
    {
        context.Response.ContentType = "text/plain";
       
        context.Response.Write(GetHtml("http://......", ""));
        context.Response.End();
    }

    //post提交
    public static string GetHtml(string posturl, string postData)
    {
        Stream outstream = null;
        Stream instream = null;
        StreamReader sr = null;
        HttpWebResponse response = null;
        HttpWebRequest request = null;
        Encoding encoding = System.Text.Encoding.GetEncoding("UTF-8");
        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, 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;
            return string.Empty;
        }
    }