1，WPF应用程序为单线程模型（STAThread)，所有UI控件都是主线程创建的，只有主线程能操作UI元素的显示。
2，其他工作线程要维护UI控件的显示，需调用主线程的Dispather，执行Invoke(同步）或BeginInvoke(异步）方法。
3，UI线程如时行耗时的操作，将使UI假死，用户体验较差。应使用后台线程进行耗时操作，并异步更新UI。
4，BackgroundWorker是WPF的一个后台工作类，代码说明一切：
前台：
<StackPanel> <ProgressBar Name="progressBar" Height="20" Width="200" Margin="10"></ProgressBar> <Button Name="btnProcess" Width="100" Click="btnProcess_Click" Margin="5">开始后台任务</Button> <Button Name="btnCancel" Width="100" Click="btnCancel_Click" Margin="5">取消后台任务</Button> </StackPanel>
后台：
public partial class MainWindow : Window { BackgroundWorker bgWorker = new BackgroundWorker(); public MainWindow() { InitializeComponent(); bgWorker.WorkerReportsProgress = true; bgWorker.WorkerSupportsCancellation = true; bgWorker.DoWork += DoWork_Handler; bgWorker.ProgressChanged += ProgressChanged_Handler; bgWorker.RunWorkerCompleted += RunWorkerCompleted_Handler; } private void btnProcess_Click(object sender, RoutedEventArgs e) { if (!bgWorker.IsBusy) { bgWorker.RunWorkerAsync(); } } private void ProgressChanged_Handler(object sender, ProgressChangedEventArgs args) { progressBar.Value = args.ProgressPercentage; } //后台线程运行的程序 private void DoWork_Handler(object sender, DoWorkEventArgs args) { BackgroundWorker worker = sender as BackgroundWorker; for (int i = 1; i <= 100; i++) { if (worker.CancellationPending) { args.Cancel = true; break; } else { worker.ReportProgress(i); //因为这在后台线程，要想直接修改UI控件，需用Invoke或BeginInvoke方法 //this.Dispatcher.Invoke(new Action(() => //{ // progressBar.Value = i; //})); Thread.Sleep(100); //因为频繁调用UI线程，为了给UI线程反应时间，这里让后台线程稍顿一下 } } } private void RunWorkerCompleted_Handler(object sender, RunWorkerCompletedEventArgs args) { progressBar.Value = 0; if (args.Cancelled) { MessageBox.Show("后台任务已经被取消。", "消息"); } else { MessageBox.Show("后台任务正常结束。", "消息"); } } private void btnCancel_Click(object sender, RoutedEventArgs e) { bgWorker.CancelAsync(); } }
