2.2 BackgroundWorker的使用介绍
BackgroundWorker 是 .NET Framework 中一个简化异步操作的组件，它位于 System.ComponentModel 命名空间下。它为开发人员提供了一种简单的方式在后台执行耗时操作，同时保持与 UI 线程的交互
主要属性以及任务如下：
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DoWork 事件：在后台线程中执行耗时操作：（不能直接调用UI控件）
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RunWorkerAsync 方法：启动后台操作
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ReportProgress 方法：报告操作进度
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ProgressChanged 事件：当进度更新时触发：（可以直接调用UI控件）
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RunWorkerCompleted 事件：当操作完成时触发（可以直接调用UI控件）
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CancellationPending 属性：检查是否请求取消
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CancelAsync 方法：请求取消操作
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IsBusy 属性：指示是否正在运行后台操作
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注意事项：
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在 DoWork 事件处理程序中不要直接访问UI控件
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如果需要传递数据，可以使用
RunWorkerAsync(object)和DoWorkEventArgs.Argument -
结果可以通过
RunWorkerCompletedEventArgs.Result传递回UI线程
例如：下面是一个wpf的小例子，仿真了开始，取消，以及汇报进度的功能。
public partial class BackgroundDemo : Window{BackgroundWorker bw;public BackgroundDemo(){InitializeComponent();bw = new BackgroundWorker();bw.WorkerReportsProgress = true;bw.WorkerSupportsCancellation = true;bw.DoWork += Bw_DoWork;bw.ProgressChanged += Bw_ProgressChanged;bw.RunWorkerCompleted += Bw_RunWorkerCompleted;btnCancel.IsEnabled = false;}private void Bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e){pbPercent.Value = 100;this.btnCancel.IsEnabled = false;this.btnStart.IsEnabled = true;if(e.Error!=null){this.tbInfo.Text = "异常" + e.Error.Message;}else if(e.Cancelled){this.tbInfo.Text = "被取消";}else{this.tbInfo.Text = "正常完成";}}private void Bw_ProgressChanged(object sender, ProgressChangedEventArgs e){this.pbPercent.Value = e.ProgressPercentage;}private void Bw_DoWork(object sender, DoWorkEventArgs e){int timer =(int) e.Argument;if (timer <= 0) timer = 20;for(int i=0;i<timer;i++){if(bw.CancellationPending){e.Cancel = true;break;}Thread.Sleep(1000);bw.ReportProgress( i*100 / timer);}}private void btnStart_Click(object sender, RoutedEventArgs e){this.btnStart.IsEnabled = false;this.btnCancel.IsEnabled = true;bw.RunWorkerAsync(10); //运行20秒this.tbInfo.Text = "开始计时中";}private void btnCancel_Click(object sender, RoutedEventArgs e){bw.CancelAsync();}}<Window x:Class="AHui_ProjectManager.Model.BackgroundDemo"xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"xmlns:d="http://schemas.microsoft.com/expression/blend/2008"xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"xmlns:local="clr-namespace:AHui_ProjectManager.Model"mc:Ignorable="d"Title="BackgroundDemo" Height="450" Width="800"><Grid><TextBlock x:Name="tbInfo" HorizontalAlignment="Left" Height="23" Background="LightBlue"Margin="0,50,0,0" VerticalAlignment="top" Width="381"/><ProgressBar x:Name="pbPercent" HorizontalAlignment="Left" Height="23" Margin="0,90,0,0" VerticalAlignment="top" Width="381"/><Button x:Name="btnStart" Content="开始" HorizontalAlignment="Left" Height="23" Margin="0,135,0,0" VerticalAlignment="top" Width="60" Click="btnStart_Click"/><Button x:Name="btnCancel" Content="取消" HorizontalAlignment="Left" Height="23" Margin="306,135,0,0" VerticalAlignment="top" Width="60" Click="btnCancel_Click"/></Grid>
</Window>