用BackgroundWorker执行后台异步操作

在桌面程序开发中，如果需要执行操作数据库或访问网络等耗时操作，会导致UI线程堵塞、界面卡死，所以应当把耗时操作放到新建线程中执行，但其他线程不能修改UI，这导致操作进度无法回馈给用户界面。

解决方法有很多，其中BackgroundWorker是.NET里用来执行多线程任务的控件，它允许编程者在一个单独的线程上执行一些操作。

代码如下：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace BGW
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        BackgroundWorker bgWorker = new BackgroundWorker();
        public MainWindow()
        {
            InitializeComponent();
            backgroundWorkerInit();
        }

        private void backgroundWorkerInit()
        {
            //使BackgroundWorker能够报告工作进度
            bgWorker.WorkerReportsProgress = true;
            //使BackgroundWorker支持异步取消
            bgWorker.WorkerSupportsCancellation = true;
            //绑定事件，在BackgroundWorker.RunWorkerAsync()时发生
            bgWorker.DoWork += Work;
            //绑定事件，在BackgroundWorker.ReportProgress(int)时发生
            bgWorker.ProgressChanged += ProgressChanged;
            //绑定事件，在BackgroundWorker完成或被终止时发生
            bgWorker.RunWorkerCompleted += RunWorkerCompleted;
        }

        private void btn_start_Click(object sender, RoutedEventArgs e)
        {
            if (!bgWorker.IsBusy)
            {
                pb.Value = 0;
                pb.Maximum = 100;
                tb.Clear();
                //开始后台异步操作
                bgWorker.RunWorkerAsync();
            }
        }

        private void btn_abort_Click(object sender, RoutedEventArgs e)
        {
            //取消后台异步操作
            bgWorker.CancelAsync();
        }

        #region BackgroundWorker事件

        private void Work(object sender, DoWorkEventArgs args)
        {
            BackgroundWorker worker = sender as BackgroundWorker;
            for (int i = 1; i <= 100; i++)
            {
                if (worker.CancellationPending)
                {
                    args.Cancel = true;
                    break;
                }
                else
                {
                    //报告进度
                    worker.ReportProgress(i);
                    //模拟费时操作
                    Thread.Sleep(100);
                }
            }
        }

        private void ProgressChanged(object sender, ProgressChangedEventArgs args)
        {
            pb.Value = args.ProgressPercentage;
            tb.Text = String.Format("第{0}项工作\n", args.ProgressPercentage) + tb.Text;
        }

        private void RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs args)
        {
            if (args.Cancelled)
            {
                MessageBox.Show("手动取消", "Message");
            }
            else
            {
                MessageBox.Show("正常结束", "Message");
            }
        }

        #endregion
    }
}

运行截图：