深入分析C#异步编程详解

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();
        }
    }
}

using System;
using System.Net;
using System.Threading;
using System.Text;
using System.IO;
// RequestState 类用于通过
// 异步调用传递数据
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;
    }
}
// ClientGetAsync 发出异步请求
class ClientGetAsync
{
    public static ManualResetEvent allDone = new ManualResetEvent(false);
    const int BUFFER_SIZE = 1024;
    public static void Main(string[] args)
    {
        if (args.Length < 1)
        {
            showusage();
            return;
        }
        // 从命令行获取 URI
        Uri HttpSite = new Uri(args[0]);
        // 创建请求对象
        HttpWebRequest wreq = (HttpWebRequest)WebRequest.Create(HttpSite);
        // 创建状态对象
        RequestState rs = new RequestState();
        // 将请求添加到状态，以便它可以被来回传递
        rs.Request = wreq;
        // 发出异步请求
        IAsyncResult r = (IAsyncResult)wreq.BeginGetResponse(new AsyncCallback(RespCallback), rs);
        // 将 ManualResetEvent 设置为 Wait，
        // 以便在调用回调前，应用程序不退出
        allDone.WaitOne();
    }
    public static void showusage()
    {
        Console.WriteLine("尝试获取 (GET) 一个 URL");
        Console.WriteLine("\r\n用法：:");
        Console.WriteLine("ClientGetAsync URL");
        Console.WriteLine("示例：:");
        Console.WriteLine("ClientGetAsync http://www.microsoft.com/net/");
    }
    private 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;
        // 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);
    }
    private 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();
            // 设置 ManualResetEvent，以便主线程可以退出
            allDone.Set();
        }
        return;
    }
}