实例：异步委托

using System;
using System.Threading;
class Program
{
    static void Main(string[] args)
    {
        Func<int, int, int> agent = new Func<int, int, int>(TakeAWhile);

        //委托使用线程池来完成异步任务
        IAsyncResult iAsync = agent.BeginInvoke(1, 3000, null, null);

        while (!iAsync.IsCompleted)
        {
            Console.Write(".");
            System.Threading.Thread.Sleep(50);
        }

        int result = agent.EndInvoke(iAsync);

        Console.WriteLine("result:{0}", result);

        Console.ReadLine();
    }

    static int TakeAWhile(int data, int ms)
    {
        Console.WriteLine("TakesAWhile started");

        System.Threading.Thread.Sleep(ms);

        Console.WriteLine("TakesAWhile completed");
        return ++data;
    }
}