用Thread和Task+async+awati实现WinFrom里面的进度条

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<int> updateUi = new Action<int>(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
    }
}