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：

  1 using System;
  2 using System.Collections.Generic;
  3 using System.ComponentModel;
  4 using System.Linq;
  5 using System.Text;
  6 using System.Threading;
  7 using System.Windows;
  8 using System.Windows.Controls;
  9 using System.Windows.Data;
 10 using System.Windows.Documents;
 11 using System.Windows.Input;
 12 using System.Windows.Media;
 13 using System.Windows.Media.Imaging;
 14 using System.Windows.Navigation;
 15 using System.Windows.Shapes;
 16
 17 namespace BGW
 18 {
 19     /// <summary>
 20     /// MainWindow.xaml 的交互逻辑
 21     /// </summary>
 22     public partial class MainWindow : Window
 23     {
 24         BackgroundWorker bgWorker = new BackgroundWorker();
 25         public MainWindow()
 26         {
 27             InitializeComponent();
 28             backgroundWorkerInit();
 29         }
 30
 31         private void backgroundWorkerInit()
 32         {
 33             //使BackgroundWorker能够报告工作进度
 34             bgWorker.WorkerReportsProgress = true;
 35             //使BackgroundWorker支持异步取消
 36             bgWorker.WorkerSupportsCancellation = true;
 37             //绑定事件，在BackgroundWorker.RunWorkerAsync()时发生
 38             bgWorker.DoWork += Work;
 39             //绑定事件，在BackgroundWorker.ReportProgress(int)时发生
 40             bgWorker.ProgressChanged += ProgressChanged;
 41             //绑定事件，在BackgroundWorker完成或被终止时发生
 42             bgWorker.RunWorkerCompleted += RunWorkerCompleted;
 43         }
 44
 45         private void btn_start_Click(object sender, RoutedEventArgs e)
 46         {
 47             if (!bgWorker.IsBusy)
 48             {
 49                 pb.Value = 0;
 50                 pb.Maximum = 100;
 51                 tb.Clear();
 52                 //开始后台异步操作
 53                 bgWorker.RunWorkerAsync();
 54             }
 55         }
 56
 57         private void btn_abort_Click(object sender, RoutedEventArgs e)
 58         {
 59             //取消后台异步操作
 60             bgWorker.CancelAsync();
 61         }
 62
 63         #region BackgroundWorker事件
 64
 65         private void Work(object sender, DoWorkEventArgs args)
 66         {
 67             BackgroundWorker worker = sender as BackgroundWorker;
 68             for (int i = 1; i <= 100; i++)
 69             {
 70                 if (worker.CancellationPending)
 71                 {
 72                     args.Cancel = true;
 73                     break;
 74                 }
 75                 else
 76                 {
 77                     //报告进度
 78                     worker.ReportProgress(i);
 79                     //模拟费时操作
 80                     Thread.Sleep(100);
 81                 }
 82             }
 83         }
 84
 85         private void ProgressChanged(object sender, ProgressChangedEventArgs args)
 86         {
 87             pb.Value = args.ProgressPercentage;
 88             tb.Text = String.Format("第{0}项工作\n", args.ProgressPercentage) + tb.Text;
 89         }
 90
 91         private void RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs args)
 92         {
 93             if (args.Cancelled)
 94             {
 95                 MessageBox.Show("手动取消", "Message");
 96             }
 97             else
 98             {
 99                 MessageBox.Show("正常结束", "Message");
100             }
101         }
102
103         #endregion
104     }
105 }

运行截图：