using System;
using System.Collections.Generic;
using System.Text;
using System.Threading;
namespace 委托的异步调用
{
public delegate void DelegateClass();//定义委托分类DelegateClass
class Starter
{
static void Main(string[] args)
{
DelegateClass del = MethodA;//定义委托对象del
DelageteStateBag state = new DelageteStateBag();//状态值state
IAsyncResult ar = del.BeginInvoke(Callback, state);// 开始委托的异步调用
if (ar.IsCompleted == true)
Console.WriteLine("MethodA completed");
else
Console.WriteLine("MethodA not completed");
ar.AsyncWaitHandle.WaitOne();
Thread.Sleep(100);
lock(state)
{
Console.WriteLine("Back in Main");
Console.WriteLine(state.message);
}
}
/// <summary>
/// 完成异步委托时的调用方法
/// </summary>
/// <param name="ar"></param>
public static void Callback(IAsyncResult ar)
{
DelageteStateBag state = (DelageteStateBag)ar.AsyncState;
lock (state)
{
Console.WriteLine("Callback Running");
((DelageteStateBag)ar.AsyncState).message = "state object modified in callback.";
}
}
public static void MethodA()
{
Console.WriteLine("MethodA running ....");
Thread.Sleep(200);
}
}
class DelageteStateBag
{
public string message;
}
}
//注：Main（）方法末尾有一个thread.sleep()语句，该语句如果被删除，在Main（）和CallBack（）
//例程间会存在竞争。因为 ar.AsyncWaitHandle.WaitOne()语句产生阻塞，当MethodA()执行完成时，阻塞消失 ，
//Main（）和CallBack（）都将继续，竞争开始。Main（）Sleep（）之后，允许CallBack（）允许为共享的state对象加锁。
