public sealed class TheTask : IBackgroundTask  {    public void Run(IBackgroundTaskInstance taskInstance)    {      var deferral = taskInstance.GetDeferral();       taskInstance.canceled+=(s,e)=>{};//当后台任务被限制执行时触发事件        taskInstance.Progress = 0;//后台任务的进度      deferral.Complete();    }

async void RegisterBackgroundTasks(){    // On Windows, RequestAccessAsync presents the user with a confirmation     // dialog that requests that an app be allowed on the lock screen.    // On Windows Phone, RequestAccessAsync does not show any user confirmation UI     // but *must* be called before registering any tasks    var access = await BackgroundExecutionManager.RequestAccessAsync();    // A ‘good‘ status return on Phone is BackgroundAccess.AllowedMayUseActiveRealTimeConnectivity    if (access == BackgroundAccessStatus.Denied)    {        // Either the user has explicitly denied background execution for this app        // or the maximum number of background apps across the system has been reached        // Display some informative message to the user...    }    BackgroundTaskBuilder taskBuilder = new BackgroundTaskBuilder();taskBuilder.Name = "MyBackgroundTask";// Many different trigger types could be used hereSystemTrigger trigger = new SystemTrigger(SystemTriggerType.TimeZoneChange, false);taskBuilder.SetTrigger(trigger);taskBuilder.AddCondition(new SystemCondition(SystemConditionType.InternetAvailable));// Entry point is the full name of our IBackgroundTask implementation// Good practice to use reflection as here to ensure correct nametaskBuilder.TaskEntryPoint = typeof(MyBackgroundTask.TheTask).FullName;BackgroundTaskRegistration registration = taskBuilder.Register();// Optionally, handle the progress/completed events of the taskregistration.Progress += registration_Progress;registration.Completed += registration_Completed;}

// AllTasks is a dictionary <Guid, IBackgroundTaskRegistration> so you can get back// to your registration by id or by posiiton, or select First if you only have one registration.var taskRegistration = BackgroundTaskRegistration.AllTasks.Values.FirstOrDefault();// We could then unregister the task, optionally cancelling any running instanceif (taskRegistration != null){    taskRegistration.Unregister(true);}// Release the progress/completed event subscriptionsregistration.Progress -= registration_Progress;registration.Completed -= registration_Completed;