//程序終點(diǎn)
//異步完成時(shí)，執(zhí)行的方法（回調(diào)方法），此方法只能有IAsyncResult一個(gè)參數(shù)，但是該參數(shù)幾乎萬(wàn)能，可以傳遞object
private void CallBackMethod(IAsyncResult ar)
{
               //從異步狀態(tài)ar.AsyncState中，獲取委托對(duì)象
               DelegateName dn = (DelegateName)ar.AsyncState;
               //輸出參數(shù)
               int i;

               //一定要EndInvoke，否則你的下場(chǎng)很慘
               string r = dn.EndInvoke(out i, ar);
               MessageBox.Show("異步完成嘍！i的值是" i.ToString() ",r的值是" r);
}

//定義與方法同簽名的委托
private delegate string DelegateName(int Num, out int Num2);

//程序入口
private void Run()
{
               //實(shí)例化委托并初賦值
               DelegateName dn = new DelegateName(MethodName);
               //輸出參數(shù)
               int i;
               //實(shí)例化回調(diào)方法
               //把AsyncCallback看成Delegate你就懂了，實(shí)際上AsyncCallback是一種特殊的Delegate，就像Event似的
               AsyncCallback acb = new AsyncCallback(CallBackMethod);
               //異步開(kāi)始
               //如果參數(shù)acb換成null則表示沒(méi)有回調(diào)方法
               //最后一個(gè)參數(shù)dn的地方，可以換成任意對(duì)象，該對(duì)象可以被回調(diào)方法從參數(shù)中獲取出來(lái)，寫成null也可以。參數(shù)dn相當(dāng)于該線程的ID，如果有多個(gè)異步線程，可以都是null，但是絕對(duì)不能一樣，不能是同一個(gè)object，否則異常
               IAsyncResult iar = dn.BeginInvoke(1, out i, acb, dn);
               //去做別的事
               //…………
}

//最后的結(jié)果應(yīng)該是：i=1，r="HelloWorld"

        /// <summary>
        /// 定義委托
        /// </summary>
        /// <returns></returns>
        public delegate bool Asyncdelegate();

        /// <summary>
        /// Callback method must have the same signature as the
        /// AsyncCallback delegate
        /// </summary>
        /// <param name="ar"></param>
        private void CallbackMethod(IAsyncResult ar)
        {
            // Retrieve the delegate.
            Asyncdelegate dlgt = (Asyncdelegate)ar.AsyncState;

            // Call EndInvoke to retrieve the results.
            dlgt.EndInvoke(ar);
        }