html的异步调用

using System;
using System.Collections.Generic;
using System.Text;
using System.Collections;
using System.Net;
using System.IO;
using System.Threading;
using System.Diagnostics;

namespace eLive.Common
{
    public class RequestState
    {
        //存储请求状态 
        const int BUFFER_SIZE = 1024;
        public StringBuilder requestData;
        public byte[] BufferRead;
        public HttpWebRequest request;
        public HttpWebResponse response;
        public Stream streamResponse;
        public RequestState()
        {
            BufferRead = new byte[BUFFER_SIZE];
            requestData = new StringBuilder("");
            request = null;
            streamResponse = null;
        }
    }

    public interface IAsyncHttpSink
    {
        void OnReadComplete(string strHtml);
        void OnReadTimeOut();
        void OnReadError();
    }

    public class AsynHttpRequest
    {
        public AsynHttpRequest(IAsyncHttpSink pSink)
        {
            _pSink = pSink;
            _strEncoding = "";
        }

        public void StartRequest(string strUrl)
        {
            try
            {
                _strEncoding = "";
                HttpWebRequest myHttpWebRequest = (HttpWebRequest)WebRequest.Create(strUrl);

                RequestState myRequestState = new RequestState();
                myRequestState.request = myHttpWebRequest;

                IAsyncResult result =
                    (IAsyncResult)myHttpWebRequest.BeginGetResponse(new AsyncCallback(RespCallback), myRequestState);

                //处理超时请求
                ThreadPool.RegisterWaitForSingleObject(result.AsyncWaitHandle, new WaitOrTimerCallback(TimeoutCallback), myHttpWebRequest, DefaultTimeout, true);

            }
            catch (WebException e)
            {
                InfoTransferHandler.Instance.ShowMsgBox(e.Message.ToString());
            }
        }

        //超时，终止请求   
        private void TimeoutCallback(object state, bool bTimeOut)
        {
            if (bTimeOut)
            {
                HttpWebRequest request = state as HttpWebRequest;
                if (request != null)
                {
                    request.Abort();
                }

                if(_pSink != null)
                {
                    _pSink.OnReadTimeOut();
                }
            }
        }

        private void RespCallback(IAsyncResult asynchronousResult)
        {
            try
            {
                //异步状态请求  
                RequestState myRequestState = (RequestState)asynchronousResult.AsyncState;
                HttpWebRequest myHttpWebRequest = myRequestState.request;
                myRequestState.response = (HttpWebResponse)myHttpWebRequest.EndGetResponse(asynchronousResult);

                //把请求读入流对象   
                Stream responseStream = myRequestState.response.GetResponseStream();
                myRequestState.streamResponse = responseStream;

                //读取Html源文件并显示到控制台
                IAsyncResult asynchronousInputRead = responseStream.BeginRead(myRequestState.BufferRead, 0, BUFFER_SIZE, new AsyncCallback(ReadCallBack), myRequestState);
                return;
            }
            catch (WebException e)
            {
                InfoTransferHandler.Instance.ShowMsgBox("异步读取文件RespCallback失败：" + e.Message);
            }
        }

        private void ReadCallBack(IAsyncResult asyncResult)
        {
            RequestState myRequestState = (RequestState)asyncResult.AsyncState;
            Stream responseStream = myRequestState.streamResponse;
            int read = responseStream.EndRead(asyncResult);
            try
            {
                //读取Html源文件
                if (read > 0)
                {
                    string strBuffer = "";
                    if(_strEncoding == "")
                    {
                        _strEncoding =  UtilCoding.DetectEncoding_Bytes(myRequestState.BufferRead).ToString();
                    }
                    
                    strBuffer = Encoding.GetEncoding(_strEncoding).GetString(myRequestState.BufferRead);
                    myRequestState.requestData.Append(strBuffer);
                    IAsyncResult asynchronousResult = responseStream.BeginRead(myRequestState.BufferRead, 0, BUFFER_SIZE, new AsyncCallback(ReadCallBack), myRequestState);
                    return;
                }
                else
                {
                   //读取完成
                    responseStream.Close();
                    if(_pSink != null)
                    {
                        _pSink.OnReadComplete(myRequestState.requestData.ToString());
                    }
                }
     
            }
            catch (Exception e)
            {
                InfoTransferHandler.Instance.ShowCommonMsg("异步读取文件ReadCallBack失败：" + e.Message);
                responseStream.Close();
                if (_pSink != null)
                {
                    _pSink.OnReadComplete(myRequestState.requestData.ToString());
                }
            }
          
        }

        private IAsyncHttpSink _pSink;
        const int BUFFER_SIZE = 1024;
        const int DefaultTimeout = 2 * 60 * 1000; //2分钟超时
        private string _strEncoding;
    }

    
}