delegate\event的方法：

类X：
using System;
using System.Collections.Generic;
using System.Windows.Forms;
using System.Text;

namespace WindowsFormsApplication1
{
    public class ClassX
    {
        public delegate void MessageDelegate(string strMsg);
        public event MessageDelegate MessageEvent;

        public void Test()
        {
            if (MessageEvent != null)
            {
                MessageEvent("类X for循环开始.");
            }

            for (int i = 0; i < 100000;i++ )
            {
                Application.DoEvents();
            }

            if (MessageEvent != null)
            {
                MessageEvent("类X for循环结束.");
            }
        }
    }
}

Form:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
 
namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }


        private ClassX cls = new ClassX();
        private void Form1_Load(object sender, EventArgs e)
        {
            cls.MessageEvent += MessageFunction;
        }

        private void MessageFunction(string strMsg)
        {
            MessageBox.Show(strMsg);
        }

        private void button1_Click(object sender, EventArgs e)
        {
            cls.Test();
        }
    }
}