多线程 Winform：摇码机

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace _112_摇奖机_多线程
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        Thread th;
        bool b = true;
        private void button1_Click(object sender, EventArgs e)
        {
            if (button1.Text == "开始")
            {
                //Thread th = new Thread(PlayGame);
                th = new Thread(PlayGame);
                th.IsBackground = true;
                b = true;
                th.Start();
                button1.Text = "停止";
            }
            else
            {
                b = false;
                button1.Text = "开始";
            }
        }
        private void PlayGame()
        {
            Random r = new Random();
            while (b)
            {
                label1.Text = r.Next(0, 10).ToString();
                label2.Text = r.Next(0, 10).ToString();
                label3.Text = r.Next(0, 10).ToString();
            }
        }
        private void Form1_Load(object sender, EventArgs e)
        {
            //取消不可跨线程访问
            Control.CheckForIllegalCrossThreadCalls = false;
        }
        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            //当你点击关闭窗口的时候，判断线程是否为null
            if (th != null)
            {
                //th.Abort();//线程被Abort后就不能被Start了
                th = null;
            }
        }
    }
}