win8中完成进度

 public sealed partial class WorkItem : Page{private IAsyncAction _threadPoolWorkItem;private ManualResetEvent _sleep = new ManualResetEvent(false);public WorkItem(){this.InitializeComponent();}// 在线程池中找一个线程去执行指定的方法，并指定其优先级private void btnCreateWorkItem_Click_1(object sender, RoutedEventArgs e){_threadPoolWorkItem = Windows.System.Threading.ThreadPool.RunAsync((threadPoolWorkItem) =>{int percent = 0; // 用于模拟执行进度（0 - 100）while (percent < 100){// 当前线程 sleep 100 毫秒_sleep.WaitOne(100);// 如果 IAsyncAction 被取消了则退出此 handler 的执行if (threadPoolWorkItem.Status == AsyncStatus.Canceled)break;percent++;var ignored = Dispatcher.RunAsync(CoreDispatcherPriority.High,() =>{lblProgress.Text = "进度：" + percent.ToString() + "%";});}},WorkItemPriority.High);// IAsyncAction 完成之后（比如任务完成了或者任务取消了）// 关于 IAsyncAction 的详细说明请参见 XamlDemo/Thread/Async_threadPoolWorkItem.Completed = new AsyncActionCompletedHandler(async (IAsyncAction threadPoolWorkItem, AsyncStatus status) =>{await Dispatcher.RunAsync(CoreDispatcherPriority.High,() =>{switch (status){case AsyncStatus.Completed:lblMsg.Text = "任务完成了";break;case AsyncStatus.Canceled:lblMsg.Text = "任务取消了";break;case AsyncStatus.Started:case AsyncStatus.Error:break;}});});lblProgress.Text = "进度：0%";lblMsg.Text = "任务开始了";}// 取消任务private void btnCancelWorkItem_Click_1(object sender, RoutedEventArgs e){if (_threadPoolWorkItem != null){_threadPoolWorkItem.Cancel();_threadPoolWorkItem = null;}}// 通过 async await 简化 ThreadPool.RunAsync() 的使用（关于 async 和 await 的详细说明请参见 XamlDemo/Thread/Async）private async void btnCreateWorkItemByAwait_Click_1(object sender, RoutedEventArgs e){lblProgress.Text = "";lblMsg.Text = "";string result = "";await Windows.System.Threading.ThreadPool.RunAsync(delegate{new ManualResetEvent(false).WaitOne(3000);result = "在线程池中找一个线程去执行指定的逻辑，然后通过 await 返回 UI 线程";});lblMsg.Text = result;}}