C# BackgroundWorker 异步控件 Demo示例

今天看别人代码时发现了C#的后台工作控件BackgroundWorker，这是一个很方便很简单的异步处理方法，于是就写个小Demo记录一下，浅显易懂，帮助自己以后回顾，更主要的是希望可以帮助到正在看这篇Demo的你。

BackgroundWorker主要有三个响应事件：
DoWork ： 后台执行逻辑代码的事件
ProgressChanged ： 响应DoWork发送的修改UI处理的事件
RunWorkerCompleted ： 当该BackgroundWorker运行结束后响应该事件

Demo:

WinForm截图：

源码：

using System;
using System.ComponentModel;
using System.Threading;
using System.Windows.Forms;

namespace BackgroundWorkerDemo
{
    public partial class Form1 : Form
    {
        private readonly BackgroundWorker _bgWorker;
        private bool _throw = false;

        public Form1()
        {
            InitializeComponent();
            _bgWorker = new BackgroundWorker();

            //允许发送消息，及调用ReportProgress()方法
            _bgWorker.WorkerReportsProgress = true;

            //允许取消该进程，及调用CancelAsync()方法
            _bgWorker.WorkerSupportsCancellation = true;

            //注册事件
            _bgWorker.DoWork += _bgWorker_DoWork;
            _bgWorker.ProgressChanged += _bgWorker_ProgressChanged;
            _bgWorker.RunWorkerCompleted += _bgWorker_RunWorkerCompleted;
        }

        /// <summary>
        /// 后台工作进程接受后调用该方法
        /// 该方法可以修改UI
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void _bgWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            if (e.Cancelled)
            {
                _txt.Text = "用户取消加载";
            }
            else if (e.Error != null)
            {
                _txt.Text = e.Error.Message;
            }
            else
            {
                _txt.Text = "加载完毕";
            }
        }

        /// <summary>
        /// 后台进程收到ReportProgress()后调用该方法
        /// 该方法可以修改UI
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void _bgWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            //修改UI,可以收到两个参数
            //e.ProgressPercentage    int
            //e.UserState             object
            _pb.Value = e.ProgressPercentage;
            _nud.Value = e.ProgressPercentage;
            _txt.Text = string.Format("当前加载 {0}%", e.ProgressPercentage);
        }

        /// <summary>
        /// 后台进程处理逻辑
        /// 该方法不能修改UI，若想修改UI就得发送ReportProgress()消息，通过ProgressChanged()方法修改
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void _bgWorker_DoWork(object sender, DoWorkEventArgs e)
        {
            for (var i = 0; i <= 100; i++)
            {
                //用户点了取消按钮，收到了CancelAsync()请求
                if (_bgWorker.CancellationPending)
                {
                    e.Cancel = true;
                    return;
                }
                //模拟抛出异常
                if (_throw)
                {
                    throw new Exception("Throw Error.");
                }

                Thread.Sleep(100);
                _bgWorker.ReportProgress(i);
            }
        }

        /// <summary>
        /// 开始按钮
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void _btnStart_Click(object sender, EventArgs e)
        {
            _throw = false;
            if (!_bgWorker.IsBusy)
            {
                _bgWorker.RunWorkerAsync();
            }
        }

        /// <summary>
        /// 取消按钮
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void _btnCancel_Click(object sender, EventArgs e)
        {
            if (_bgWorker.IsBusy)
            {
                _bgWorker.CancelAsync();
            }
        }

        /// <summary>
        /// 抛异常按钮
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void _btnThrow_Click(object sender, EventArgs e)
        {
            _throw = true;
        }
    }
}