C# 异步发送HttpWebRequest

using System;

 namespace ConsoleApplication1
 {
     class Class1
     {
         //声明委托
         public delegate void AsyncEventHandler();
 
         //异步方法
         void Event1()
        {
            Console.WriteLine("Event1 Start");
            System.Threading.Thread.Sleep(4000);
            Console.WriteLine("Event1 End");
        }

        // 同步方法
        void Event2()
        {
            Console.WriteLine("Event2 Start");
            int i=1;
            while(i<1000)
            {
                i=i+1;
                Console.WriteLine("Event2 "+i.ToString());
            }
            Console.WriteLine("Event2 End");
        }

        [STAThread]
        static void Main(string[] args)
        {
            long start=0;
            long end=0;
            Class1 c = new Class1();
            Console.WriteLine("ready");
            start=DateTime.Now.Ticks;

            //实例委托
            AsyncEventHandler asy = new AsyncEventHandler(c.Event1);
            //异步调用开始，没有回调函数和AsyncState,都为null
            IAsyncResult ia = asy.BeginInvoke(null, null);
            //同步开始，
            c.Event2();
            //异步结束，若没有结束，一直阻塞到调用完成，在此返回该函数的return，若有返回值。

           
            asy.EndInvoke(ia);

            //都同步的情况。
            //c.Event1();
            //c.Event2();
           
            end =DateTime.Now.Ticks;
            Console.WriteLine("时间刻度差="+ Convert.ToString(end-start) );
            Console.ReadLine();
        }
    }
}

 

HttpWebRequest

ClientGetAsync.cs

using System;
using System.Net;
using System.IO;

/// <summary>
/// Summary description for ClientGetAsync
/// </summary>
public class ClientGetAsync
{
    public ClientGetAsync()
    {

    }

    public static void SendGetAsync(string url)
    {
        // 从命令行获取 URI
        Uri HttpSite = new Uri(url);

        // 创建请求对象
        HttpWebRequest wreq = WebRequest.Create(HttpSite) as HttpWebRequest;
        // 创建状态对象
        RequestState rs = new RequestState();
        rs.Request = wreq;
        IAsyncResult ar = wreq.BeginGetResponse(new AsyncCallback(RespCallback), rs);
    }

    public static void RespCallback(IAsyncResult ar)
    {
        // 从异步结果获取 RequestState 对象
        RequestState rs = (RequestState)ar.AsyncState;

        // 从 RequestState 获取 HttpWebRequest
        HttpWebRequest req = rs.Request;

        // 调用 EndGetResponse 生成 HttpWebResponse 对象
        // 该对象来自上面发出的请求
        HttpWebResponse resp = (HttpWebResponse)req.EndGetResponse(ar);

        // 既然我们拥有了响应，就该从
        // 响应流开始读取数据了
        Stream ResponseStream = resp.GetResponseStream();

        // 该读取操作也使用异步完成，所以我们
        // 将要以 RequestState 存储流
        rs.ResponseStream = ResponseStream;
        System.Threading.Thread.Sleep(10000);
        // 请注意，rs.BufferRead 被传入到 BeginRead。
        // 这是数据将被读入的位置。
        IAsyncResult iarRead = ResponseStream.BeginRead(rs.BufferRead, 0, BUFFER_SIZE, new AsyncCallback(ReadCallBack), rs);
    }


    public static void ReadCallBack(IAsyncResult asyncResult)
    {
        // 从 asyncresult 获取 RequestState 对象
        RequestState rs = (RequestState)asyncResult.AsyncState;

        // 取出在 RespCallback 中设置的 ResponseStream
        Stream responseStream = rs.ResponseStream;

        // 此时 rs.BufferRead 中应该有一些数据。
        // 读取操作将告诉我们那里是否有数据
        int read = responseStream.EndRead(asyncResult);

        if (read > 0)
        {
            // 准备 Char 数组缓冲区，用于向 Unicode 转换
            Char[] charBuffer = new Char[BUFFER_SIZE];

            // 将字节流转换为 Char 数组，然后转换为字符串
            // len 显示多少字符被转换为 Unicode
            int len = rs.StreamDecode.GetChars(rs.BufferRead, 0, read, charBuffer, 0);
            String str = new String(charBuffer, 0, len);

            // 将最近读取的数据追加到 RequestData stringbuilder 对象中，
            // 该对象包含在 RequestState 中
            rs.RequestData.Append(str);


            // 现在发出另一个异步调用，读取更多的数据
            // 请注意，将不断调用此过程，直到
            // responseStream.EndRead 返回 -1
            IAsyncResult ar = responseStream.BeginRead(rs.BufferRead, 0, BUFFER_SIZE, new AsyncCallback(ReadCallBack), rs);
        }
        else
        {
            if (rs.RequestData.Length > 1)
            {
                // 所有数据都已被读取，因此将其显示到控制台
                string strContent;
                strContent = rs.RequestData.ToString();
                Console.WriteLine(strContent);
            }

            // 关闭响应流
            responseStream.Close();

        }
        return;
    }

    public static int BUFFER_SIZE = 1024;
}

 

RequestState.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Text;
using System.IO;
using System.Net;

/// <summary>
/// Summary description for RequestState
/// </summary>
public class RequestState
{
    const int BUFFER_SIZE = 1024;
    public StringBuilder RequestData;
    public byte[] BufferRead;
    public HttpWebRequest Request;
    public Stream ResponseStream;
    // 创建适当编码类型的解码器
    public Decoder StreamDecode = Encoding.UTF8.GetDecoder();

    public RequestState()
    {
        BufferRead = new byte[BUFFER_SIZE];
        RequestData = new StringBuilder("");
        Request = null;
        ResponseStream = null;
    }
}

 

调用

ClientGetAsync.SendGetAsync("http://www.amazon.com/");