等待异步委托结果的三种方法

1.创建线程的一种简单方法是定义一个委托，异步调用它。一种技术是投票，检查委托是否完成了任务。 using System;using System.Collections.Generic;using System.Diagnostics;using System.Linq;using System.Text;using System.Threading;
namespace ConsolTread{    class Program    {        //委托使用线程池来完成异步任务C#高级编程中代码        static int TakeAAwhile(int data,int ms)        {            Console.WriteLine("takeaawhile started");            Thread.Sleep(ms);            Console.WriteLine("takeaawhile completed");            return ++data;        }        //创建委托        public delegate int TakeAAwhileDelegate(int data, int ms);         static void Main(string[] args)        {            TakeAAwhileDelegate dl = TakeAAwhile;            //IAsyncResult可以获得委托信息，并验证委托是否完成了任务。            IAsyncResult ar=dl.BeginInvoke(1,700,null,null);            while(!ar.IsCompleted)            {                Console.WriteLine(".");                Thread.Sleep(50);            }            int result = dl.EndInvoke(ar);            Console.WriteLine("result:{0}", result);
        }    }} 

 第二种是使用与IAsyncResult相关的等待句柄

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Diagnostics;

namespace asyThread
{
  
        class Program
        {
            //委托使用线程池来完成异步任务C#高级编程中代码
            static int TakeAAwhile(int data, int ms)
            {
                Console.WriteLine("takeaawhile started");
                Thread.Sleep(ms);
                Console.WriteLine("takeaawhile completed");
                return ++data;
            }
            //创建委托
            public delegate int TakeAAwhileDelegate(int data, int ms);

            static void Main(string[] args)
            {
                //等待句柄
                TakeAAwhileDelegate dl = TakeAAwhile;
                IAsyncResult ar = dl.BeginInvoke(1, 3000, null, null);
                while(true)
                {
                    Console.Write(".");
                    if (ar.AsyncWaitHandle.WaitOne(50,false))
                    {
                        Console.WriteLine("Can get the result");
                        break;
                    }
                }
                int result = dl.EndInvoke(ar);
                Console.WriteLine("result:{0}", result);
            }
        }  

} 

第三种是使用异步回调方法

using System;
using System.Collections.Generic;
using System.Text;
using System.Threading;
using System.Diagnostics;

namespace Wrox.ProCSharp.Threading
{
   class Program
   {
      static int TakesAWhile(int data, int ms)
      {
         Console.WriteLine("TakesAWhile started");
         Thread.Sleep(ms);
         Console.WriteLine("TakesAWhile completed");
         return ++data;
      }

      public delegate int TakesAWhileDelegate(int data, int ms);

      static void Main()
      {

         TakesAWhileDelegate d1 = TakesAWhile;
         d1.BeginInvoke(1, 3000,
            ar =>
               {
                  int result = d1.EndInvoke(ar);
                  Console.WriteLine("result: {0}", result);
               },
            null);
         for (int i = 0; i < 100; i++)
         {
            Console.Write(".");
            Thread.Sleep(50);
         }
         
      }

      static void TakesAWhileCompleted(IAsyncResult ar)
      {
         if (ar == null) throw new ArgumentNullException("ar");
         TakesAWhileDelegate d1 = ar.AsyncState as TakesAWhileDelegate;
         Trace.Assert(d1 != null, "Invalid object type");

         int result = d1.EndInvoke(ar);
         Console.WriteLine("result: {0}", result);
      }
   }

}