win10通用应用程序后台任务未运行

我有一个精简的Windows 10通用应用程序（VS2015），它的后台任务本应更新实时互动程序，但似乎不起作用。我创建了一个带有两个按钮的基本XAML页面："启用"answers"禁用"。启用按钮注册后台任务，禁用按钮取消注册。

主应用程序（App6）MainPage.cs文件的代码：

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Windows.ApplicationModel.Background;
using Windows.UI.Popups;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
namespace App6
{
    public sealed partial class MainPage : Page
    {
        private string TN = "APP6_TASK";
        private string TEP = "App6BackgroundTask2.BackgroundTaskHelper";
        public MainPage()
        {
            InitializeComponent();
        }
        private void Enable(object sender, RoutedEventArgs e)
        {
            try { RegisterTask(); }
            catch(Exception ex) { ShowDialog(ex.ToString()); }
        }
        private void Disable(object sender, RoutedEventArgs e)
        {
            try { UnregisterTask(); }
            catch (Exception ex) { ShowDialog(ex.ToString()); }
        }
        private async void ShowDialog(string message)
        {
            var dlg = new MessageDialog(message);
            await dlg.ShowAsync();
        }
        public void RegisterTask()
        {
            //no need to register a task that already exists
            if (GetTask()) { return; }
            var backgroundTaskBuilder = new BackgroundTaskBuilder() { Name = TN, TaskEntryPoint = TEP };
            backgroundTaskBuilder.SetTrigger(new TimeTrigger(15, false));
            backgroundTaskBuilder.Register();
        }
        public void UnregisterTask()
        {
            var task = new KeyValuePair<Guid, IBackgroundTaskRegistration>();
            //no need to unregister a task that doesn't exist
            if (GetTask(ref task))
            {
                task.Value.Unregister(true);
            }
        }
        public bool GetTask()
        {
            foreach (var t in BackgroundTaskRegistration.AllTasks)
            {
                if (t.Value.Name == TN)
                {
                    return true;
                }
            }
            return false;
        }
        public bool GetTask(ref KeyValuePair<Guid, IBackgroundTaskRegistration> task)
        {
            foreach (var t in BackgroundTaskRegistration.AllTasks)
            {
                if (t.Value.Name == TN)
                {
                    task = t;
                    return true;
                }
            }
            return false;
        }
    }
}

我打开Package.AppManifest文件，在"Declarations"选项卡下添加"Background Tasks"声明，并选择"Timer"任务类型。对于入口点，我输入了

App6BackgroundTask2.BackgroundTaskHelper

我在解决方案中添加了第二个项目，并从主要应用程序中引用了它。该项目中唯一的类（BackgroundTaskHelper.cs）的代码是：

using System;
using System.Diagnostics;
using Windows.ApplicationModel.Background;
using Windows.Data.Xml.Dom;
using Windows.UI.Notifications;
namespace App6BackgroundTask2
{
    public sealed class BackgroundTaskHelper : IBackgroundTask
    {
        public void Run(IBackgroundTaskInstance taskInstance)
        {
            var backgroundTaskDeferral = taskInstance.GetDeferral();
            try { UpdateTile(); }
            catch (Exception ex){ Debug.WriteLine(ex); }
            finally { backgroundTaskDeferral.Complete(); }
        }
        private void UpdateTile()
        {
            var now = DateTime.Now.ToString("HH:mm:ss");
            var xml =
                "<tile>" +
                "  <visual>" +
                "    <binding template='TileSmall'>" +
                "      <text>" + now + "</text>" +
                "    </binding>" +
                "    <binding template='TileMedium'>" +
                "      <text>" + now + "</text>" +
                "    </binding>" +
                "    <binding template='TileWide'>" +
                "      <text>" + now + "</text>" +
                "    </binding>" +
                "    <binding template='TileLarge'>" +
                "      <text>" + now + "</text>" +
                "    </binding>" +
                "  </visual>" +
                "</tile>";
            var tileDom = new XmlDocument();
            tileDom.LoadXml(xml);
            var tile = new TileNotification(tileDom);
            TileUpdateManager.CreateTileUpdaterForApplication().Update(tile);
        }
    }
}

我已经在调试模式下运行了主应用程序，单击"启用"以注册后台任务，从Debug.Location工具栏暂停了任务，并验证了任务的run方法是否执行并且没有引发异常。当我检查"开始"菜单时，磁贴会按预期更新。当我关闭应用程序并等待时，互动程序再也不会更新。

我卸载了该应用程序，重新编译为Release，并从开始菜单运行它（不在IDE中运行）。我点击"启用"按钮注册后台任务，关闭应用程序并等待。互动程序从未更新。

我好像错过了什么，但我不知道是什么。如有任何协助，我们将不胜感激。Thanx

public async Task RegisterTask()
{
    var backgroundAccessStatus = await BackgroundExecutionManager.RequestAccessAsync();
    if (backgroundAccessStatus == BackgroundAccessStatus.Denied) { return; }
    if (GetTask()) { return; }
    var timeTrigger = new TimeTrigger(15, false);
    var backgroundTaskBuilder = new BackgroundTaskBuilder();
    backgroundTaskBuilder.Name = TASK_NAME;
    backgroundTaskBuilder.TaskEntryPoint = typeof(BackgroundTileTimerTask.BackgroundTask).FullName;
    backgroundTaskBuilder.SetTrigger(timeTrigger);
    backgroundTaskBuilder.Register();
}