c# 委托的一种写法

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Threading;

namespace WindowsApplication19
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        //声明事件委托
        private delegate void delUpdate(string s);


        void update(string s)
        {
            if (label1.InvokeRequired) // 当在其它线程中更新LABEL控件时,为true;否则为false
            {
                delUpdate du = new delUpdate(update);

                //指定委托.程序运行到这里,会再执行一次update(),但
                //label1.InvokeRequired值为false,相当如在主线程中执行更新动作
                label1.Invoke(du, new object[] { s});
            }
            else
            {
                //在主线程中执行更新动作
                label1.Text = s;
            }
        }

        void refresh()
        {
            for (int i = 0; i < 10000; i++)
            {
                update(i.ToString());
            }

            thd.Abort();
            thd = null;
        }

        Thread thd;
        private void button1_Click(object sender, EventArgs e)
        {
            thd = new Thread(refresh);
            thd.Start();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            update("hello");
        }
    }
}