using System;
using System.Threading;

namespace AsyncDelegateDemo
{
  delegate void AsyncFoo(int i);
  class Program
  {
    ///<summary>
    /// 输出当前线程的信息
    ///</summary>
   ///<param name="name">方法名称</param>

    static void PrintCurrThreadInfo(string name)
    {
      Console.WriteLine("Thread Id of " + name+ " is: " + Thread.CurrentThread.ManagedThreadId+ ", current thread is "
      + (Thread.CurrentThread.IsThreadPoolThread ? "" : "not ")
      + "thread pool thread.");
    }

    ///<summary>
    /// 测试方法，Sleep一定时间
    ///</summary>
    ///<param name="i">Sleep的时间</param>
    static void Foo(int i)
    {
       PrintCurrThreadInfo("Foo()");
       Thread.Sleep(i);
    }

    ///<summary>
    /// 投递一个异步调用
    ///</summary>
    static void PostAsync()
    {
      AsyncFoo caller = new AsyncFoo(Foo);
      caller.BeginInvoke(1000, new AsyncCallback(FooCallBack), caller);
    }

    static void Main(string[] args)
    {
      PrintCurrThreadInfo("Main()");
      for(int i = 0; i < 10 ; i++)
      {
         PostAsync();
      }
      Console.ReadLine();
    }

    static void FooCallBack(IAsyncResult ar)
    {
      PrintCurrThreadInfo("FooCallBack()");
      AsyncFoo caller = (AsyncFoo) ar.AsyncState;
      caller.EndInvoke(ar);
    }
  }
}  

Thread Id of Main() is: 1, current thread is not thread pool thread.
Thread Id of Foo() is: 3, current thread is thread pool thread.
Thread Id of FooCallBack() is: 3, current thread is thread pool thread.
Thread Id of Foo() is: 3, current thread is thread pool thread.
Thread Id of Foo() is: 4, current thread is thread pool thread.
Thread Id of Foo() is: 5, current thread is thread pool thread.
Thread Id of FooCallBack() is: 3, current thread is thread pool thread.
Thread Id of Foo() is: 3, current thread is thread pool thread.
Thread Id of FooCallBack() is: 4, current thread is thread pool thread.
Thread Id of Foo() is: 4, current thread is thread pool thread.
Thread Id of Foo() is: 6, current thread is thread pool thread.
Thread Id of FooCallBack() is: 5, current thread is thread pool thread.
Thread Id of Foo() is: 5, current thread is thread pool thread.
Thread Id of Foo() is: 7, current thread is thread pool thread.
Thread Id of FooCallBack() is: 3, current thread is thread pool thread.
Thread Id of Foo() is: 3, current thread is thread pool thread.
Thread Id of FooCallBack() is: 4, current thread is thread pool thread.
Thread Id of FooCallBack() is: 6, current thread is thread pool thread.
Thread Id of FooCallBack() is: 5, current thread is thread pool thread.
Thread Id of FooCallBack() is: 7, current thread is thread pool thread.
Thread Id of FooCallBack() is: 3, current thread is thread pool thread.