新建WinFrom项目，在界面上添加两个按钮 

分别用Thread和Task实现进度条效果 

using System;using System.Threading;using System.Threading.Tasks;using System.Windows.Forms;namespace WindowsFormsApp1{    public partial class Form1 : Form    {        public Form1()        {            InitializeComponent();        }        //普通Thread实现进度条        private void button1_Click(object sender, EventArgs e)        {            Console.WriteLine("主线程开始");            new Thread(DoProcessing).Start(); //没有使用线程池，每次调用都开启新线程            //ThreadPool.QueueUserWorkItem(DoProcessing);//使用线程池，重复开启的时候回去线程池拿空闲的线程            Console.WriteLine("主线程结束");        }        //在方法上加上 async         private async void button2_Click(object sender, EventArgs e)        {            await UpdateUi2();            //async.await的语法糖为我们带来了更好的异步编程体验        }        #region Thread        void UpdateUi(int percent)        {            //UI操作            button1.Text = string.Format("{0}%", percent);        }        void DoProcessing(object obj)        {            for (int i = 0; i <= 5; ++i)            {                Thread.Sleep(500);                Console.WriteLine("---------- " + i);                Action
     
       updateUi = new Action
      
       (UpdateUi);                this.Invoke(updateUi, i);            }        }        #endregion        #region task,async,await        private static int _percent = 0;        int DoProcessing2()        {            Console.WriteLine("Thread id in DoProcessing: {0}", Thread.CurrentThread.ManagedThreadId);            Thread.Sleep(500);            return ++_percent;        }        async Task UpdateUi2()        {            _percent = 0;            button1.Text = string.Format("{0}%", 0);            while (_percent < 5)            {                //await起到释放主线程的作用                int percent = await Task.Run(() => DoProcessing2());                //在子线程处理完成后，又请求主线程继续下面的代码，下面的代码相当于Thread的回调                button2.Text = string.Format("{0}%", percent);            }        }        #endregion        #region 参考        private void button3_Click(object sender, EventArgs e)        {            Thread.Sleep(3000); //堵塞主线程            button1.Text = string.Format("99%");        }        #endregion    }}