C# HttpWebRequest人异步访问

----------------------------Un Test-------------------------
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.Threading;
using System.IO;


namespace WebReqHtml
{
    internal class WebReqState
    {
        public byte[] Buffer;
        public MemoryStream ms;
        public const int BufferSize = 1024;
        public Stream OrginalStream;
        public HttpWebResponse WebResponse;
    
        public WebReqState()
        {
            Buffer = new byte[1024];
            ms = new MemoryStream();
        }
    }
    public delegate  void  ReadDataComplectedEventHandler(byte[] data);

    class HtmlFromWebReq
    {

        private Uri url;

        public event ReadDataComplectedEventHandler OnReadDataComplected;

        public HtmlFromWebReq(string absoluteUrl)
        {
            url = new Uri(absoluteUrl);
        }
        protected void readDataCallback(IAsyncResult ar)
        {

            WebReqState rs = ar.AsyncState as WebReqState;
            int read = rs.OrginalStream.EndRead(ar);
            if (read > 0)
            {
                rs.ms.Write(rs.Buffer, 0, read);
                rs.OrginalStream.BeginRead(rs.Buffer, 0, WebReqState.BufferSize, new AsyncCallback(readDataCallback), rs);
            }
            else

            {
                rs.OrginalStream.Close();
                rs.WebResponse.Close();
                if (OnReadDataComplected != null)
                {
                    OnReadDataComplected(rs.ms.ToArray());
                }
            }

        }

        protected void responseCallback(IAsyncResult ar)
        {
            HttpWebRequest req = ar.AsyncState as HttpWebRequest;
            if (req == null)
                return;
            HttpWebResponse response = req.EndGetResponse(ar) as HttpWebResponse;
            if (response.StatusCode!= HttpStatusCode.OK)
            {
                response.Close();
                return;
            }
            WebReqState st=new WebReqState();
            st.WebResponse = response;
            Stream repsonseStream = response.GetResponseStream();
            st.OrginalStream = repsonseStream;
            repsonseStream.BeginRead(st.Buffer, 0, WebReqState.BufferSize, new AsyncCallback(readDataCallback), st);


        }

        public void BeginCreateHtml()
        {
            HttpWebRequest req = HttpWebRequest.Create(url.AbsoluteUri) as HttpWebRequest;
            req.BeginGetResponse( new AsyncCallback(responseCallback), req);
            
        }
         
    }
}