C#线程处理系列之线程池中的I/O线程

二、I/O线程实现对请求的异步

我们同样可以利用I/O线程来模拟对浏览器对服务器请求的异步操作，在.net类库中的WebRequest类提供了异步请求的支持，

下面就来演示下如何实现请求异步：

using System;
using System.Net;
using System.Threading;

namespace RequestSample
{
  class Program
  {
    static void Main(string[] args)
    {
      ThreadPool.SetMaxThreads(1000, 1000);
      PrintMessage("Main Thread start");

      // 发出一个异步Web请求
      WebRequest webrequest =WebRequest.Create("http://www.easck.com/");
      webrequest.BeginGetResponse(ProcessWebResponse, webrequest);

      Console.Read();
    }

    // 回调方法
    private static void ProcessWebResponse(IAsyncResult result)
    {
      Thread.Sleep(500);
      PrintMessage("Asynchronous Method start");

      WebRequest webrequest = (WebRequest)result.AsyncState;
      using (WebResponse webresponse = webrequest.EndGetResponse(result))
      {      
        Console.WriteLine("Content Length is : "+webresponse.ContentLength);
      }
    }

    // 打印线程池信息
    private static void PrintMessage(String data)
    {
      int workthreadnumber;
      int iothreadnumber;

      // 获得线程池中可用的线程，把获得的可用工作者线程数量赋给workthreadnumber变量
      // 获得的可用I/O线程数量给iothreadnumber变量
      ThreadPool.GetAvailableThreads(out workthreadnumber, out iothreadnumber);

      Console.WriteLine("{0}n CurrentThreadId is {1}n CurrentThread is background :{2}n WorkerThreadNumber is:{3}n IOThreadNumbers is: {4}n",
        data,
        Thread.CurrentThread.ManagedThreadId,
        Thread.CurrentThread.IsBackground.ToString(),
        workthreadnumber.ToString(),
        iothreadnumber.ToString());
    }
  }
}