WPF进度条显示问题求解。

Question

 BackgroundWorker worker;        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            worker = new BackgroundWorker();
            worker.WorkerReportsProgress = true;
            worker.WorkerSupportsCancellation = true;
            worker.DoWork += new DoWorkEventHandler(worker_DoWork);
            worker.ProgressChanged += new ProgressChangedEventHandler(worker_ProgressChanged);
            worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
            progressBar.Value = 0;
            worker.RunWorkerAsync();
        }
        void worker_DoWork(object sender, DoWorkEventArgs e)
        {
            BackgroundWorker w = sender as BackgroundWorker;
            for (int i = 0; i < 100; i++)
            {
                System.Threading.Thread.Sleep(1);//时间为毫秒
                w.ReportProgress(i);
            }
        }
        void worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            progressBar.Value = e.ProgressPercentage;
        }
        void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            progressBar.Visibility = Visibility.Hidden;
        }