C# 多线程的进度条

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Threading;

namespace WindowsFormsApp4
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private async void button1_Click(object sender, EventArgs e)
        {
            var progressHandler = new Progress<string>(value =>
            {
                label2.Text = "当前值：" + value;
                progressBar1.Value = Convert.ToInt32(value);
            });
            var progress = progressHandler as IProgress<string>;
            await Task.Run(() =>
            {
                for (int i = 0; i != 100; ++i)
                {
                    if (progress != null)
                        progress.Report(i.ToString());
                    Thread.Sleep(100);
                }
            });
            label2.Text = "Completed.";
        }
    }
}