匿名委托问题

Question

下面是一个窗体程序代码，一个按钮，一个label。为什么一调试就报错：下面所示线程间操作无效: 从不是创建控件“label1”的线程访问它。不调试没错，匿名委托应该能访问包含它的类变量的啊!
        private void button1_Click(object sender, EventArgs e)
        {
            new System.Threading.Thread(delegate()
            {
                this.label1.Text = "1";                System.Threading.Thread.Sleep(5000);                this.label1.Text = "2";
            })
            .Start();
        }

Answer 1

        private void button1_Click(object sender, EventArgs e)
        {
            new System.Threading.Thread(delegate()
            {
                this.Invoke(new MethodInvoke(delegate
                {
              
                this.label1.Text = "1";                System.Threading.Thread.Sleep(5000);                this.label1.Text = "2";
                }));
            })
            .Start();
        }

Answer 2

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 WindowsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();        }
        private void button1_Click(object sender, EventArgs e)
        {
            new System.Threading.Thread(delegate()
            {
                this.Invoke(new MethodInvoker(delegate
                 {                     this.label1.Text = "1";                     System.Threading.Thread.Sleep(5000);                     this.label1.Text = "2";
                 }));
            })
            .Start();         }    }
}