BackgroundWorker的使用一二（可视化编程，开始后台工作，报告进度，取消后台工作等）

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Windows.Forms;

namespace VisibleBackgroundWorker
{
    public partial class Form1 : Form
    {
        int total = 100;
        
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }
        /// <summary>
        /// 后台作业代码
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e">e.Cancel用于返回终止标志，e.Result用于返回数据，e.Argument为传入的参数</param>
        private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
        {
            List<string> itemList = new List<string>();
            for (int i = 0; i < total; i++)
            {
                if (backgroundWorker1.CancellationPending)
                { //如果执行了CancelAsync()                   
                    e.Cancel = true; //设置后台作业取消标志
                    return;
                }
                string item = "item " + i.ToString();
                backgroundWorker1.ReportProgress(i,item);
                itemList.Add(item);
                System.Threading.Thread.Sleep(500);
            }
            e.Result = itemList;//返回结果
            
        }
        /// <summary>
        /// 进度报告事件，可用于显示进度、中间结果等
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e">e.ProgressPercentage为进度，e.UserState可定义的回传数据</param>
        private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
        { 
            int p = e.ProgressPercentage;
            string item = e.UserState as string;
            label1.Text = "Progress:" + p.ToString();
            listBox1.Items.Add(item);
            
        }
        /// <summary>
        /// 后台作业完成事件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e">e.Cancel为是否被终止的标志</param>
        private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            if(e.Cancelled)
            {//中途终止
                label1.Text = "Cancel!";
            }
            else
            {//正常结束
                label1.Text = "Complete!";
            }
            
            listBox2.Items.AddRange((e.Result as List<string>).ToArray());
        }

        private void button1_Click(object sender, EventArgs e)
        {   //终止后台作业标志（设置CancellationPending标志）
            backgroundWorker1.CancelAsync();
        }

        private void btnGo_Click(object sender, EventArgs e)
        {//开始后台作业
            int arg = 1;//传到后台作业的参数
            backgroundWorker1.RunWorkerAsync(arg);
        }
    }
}