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.