ItemGridView ItemClick on Windows Store App

我在Windows 8商店应用程序上。在这个项目中。我需要将数据发送到另一个页面。计划是，我在 MainPage.xaml 中有一个 ItemGridView，我单击新闻的图像，我需要将该新闻的文章 ID 发送到下一页，并且必须使用该 ID 创建一篇文章。

我用这个做了这个Windows Phone 8应用程序;

private void MainLongListSelectorSelectionChanged(object sender, SelectionChangedEventArgs e)
{
            NavigationService.Navigate(
                new Uri(
                    "/DetailsPage.xaml?selectedIndex=" +
                    ((MyWebApi.Headline) MainLongListSelector.SelectedItem).ARTICLEID, UriKind.Relative));
}

在赢商店应用程序中，我尝试这个;

private void itemGridView_ItemClick(object sender, ItemClickEventArgs e)
{
            this.Frame.Navigate(typeof (BasicPage1),
                ((MyWebApi.MainPageHeadline) itemGridView.SelectedItem).ARTICLEID);
}

我也尝试过这样;

private void itemGridView_ItemClick(object sender, ItemClickEventArgs e)
        {
            var articleid = ((MyWebApi.MainPageHeadline) itemGridView.SelectedItem).ARTICLEID;
            this.Frame.Navigate(typeof (BasicPage1), articleid);
        }

但我明白

"对象引用未设置为对象的实例。"

在行的末尾。

我无法用这个获得 ID 的值。还有其他建议吗？

谢谢。

更新：

这是 MainPage.xaml.cs;

public sealed partial class MainPage : try012.Common.LayoutAwarePage
    {
        private string _json = "";
        private MyWebApi.RootObject Headlines { get; set; }
        public MainPage()
        {
            this.InitializeComponent();
        }
        protected override void LoadState(Object navigationParameter, Dictionary<String, Object> pageState)
        {
        }
        protected override void OnNavigatedTo(NavigationEventArgs e)
        {
            const string urlt = "MyWebApiURL";
            var hWebRequestt = (HttpWebRequest)WebRequest.Create(urlt);
            hWebRequestt.Method = "GET";
            hWebRequestt.BeginGetResponse(MainLongListSelectorLoadCompletedt, hWebRequestt);
        }
        private void MainLongListSelectorLoadCompletedt(IAsyncResult ar)
        {
            var request = (HttpWebRequest)ar.AsyncState;
            var response = (HttpWebResponse)request.EndGetResponse(ar);
            using (var streamReader = new StreamReader(response.GetResponseStream()))
            {
                _json = streamReader.ReadToEnd();
                Headlines = JsonConvert.DeserializeObject<MyWebApi.RootObject>(_json);
            }
            if (Headlines.MainPageHeadline.Count > 0)
                Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
                {
                    itemGridView.ItemsSource = Headlines.MainPageHeadline.ToList();
                });
        }
        private void itemGridView_ItemClick(object sender, ItemClickEventArgs e)
        {
            this.Frame.Navigate(typeof(BasicPage1),((MyWebApi.MainPageHeadline)e.ClickedItem).ARTICLEID);
        }

    }

这是BasicPage1.xaml.cs;

public sealed partial class BasicPage1 : try012.Common.LayoutAwarePage
    {
        public BasicPage1()
        {
            this.InitializeComponent();
        }
        protected override void LoadState(Object navigationParameter, Dictionary<String, Object> pageState)
        {
        }
        protected override void SaveState(Dictionary<String, Object> pageState)
        {
        }
    }

private void itemGridView_ItemClick(object sender, ItemClickEventArgs e)
{
    this.Frame.Navigate(typeof (BasicPage1),
        ((MyWebApi.MainPageHeadline) e.ClickedItem).ARTICLEID);
}

 protected override void OnNavigatedTo(NavigationEventArgs e)
    {
        base.OnNavigatedTo(e);
        const string urlt = "MyWebApiURL";
        var hWebRequestt = (HttpWebRequest)WebRequest.Create(urlt);
        hWebRequestt.Method = "GET";
        hWebRequestt.BeginGetResponse(MainLongListSelectorLoadCompletedt, hWebRequestt);
    }