背景任务延期.完成

我的问题是，deferral.complete()方法到底是什么，这个方法调用事件task.Compledet吗，或者有没有办法从我的类BackgroundSyncer中的BackgroundTaskSyncer调用方法？？？？当我运行Programm时，我会从BackgroundTaskSyncer中执行run方法，但在其他类中什么都不做？？

    namespace NotificationTask
            {
                public sealed class BackgroundTaskSyncer : IBackgroundTask
                {
                    public void Run(IBackgroundTaskInstance taskInstance)
                    {
                        BackgroundTaskDeferral deferral = taskInstance.GetDeferral();
                        deferral.Complete();
                    }
                }
                }
    namespace Services
    {
    public static class BackgroundSync
        {
    private static async Task RegisterBackgroundTask()
            {
                try
                {
                    BackgroundAccessStatus status = await BackgroundExecutionManager.RequestAccessAsync();
                    if (status == BackgroundAccessStatus.AllowedWithAlwaysOnRealTimeConnectivity || status == BackgroundAccessStatus.AllowedMayUseActiveRealTimeConnectivity)
                    {
                        bool isRegistered = BackgroundTaskRegistration.AllTasks.Any(x => x.Value.Name == "Notification task");
                        if (!isRegistered)
                        {
                            BackgroundTaskBuilder builder = new BackgroundTaskBuilder
                            {
                                Name = "Notification task",
                                TaskEntryPoint =
                                    "NotificationTask.BackgroundTaskSyncer"
                            };
                            builder.SetTrigger(new TimeTrigger(15, false));
                            builder.AddCondition(new SystemCondition(SystemConditionType.InternetAvailable));
                            BackgroundTaskRegistration task = builder.Register();
                            task.Completed += new BackgroundTaskCompletedEventHandler(OnCompleted);
                            task.Progress += new BackgroundTaskProgressEventHandler(OnProgress);
                        }
                    }
                }
                catch (Exception ex)
                {
                    System.Diagnostics.Debug.WriteLine("The access has already been granted");
                }
            }
    private static void OnCompleted(IBackgroundTaskRegistration task, BackgroundTaskCompletedEventArgs args)
            {
                ToTheBackGroundWork();
            }