wp8 c#中联系人查询的数据绑定结果出现异常

我一直试图在我的windowsphone 8应用程序中嵌入一个联系人选择器。这个想法很简单。。。显示联系人，允许用户点击他们希望保存以供我的应用程序使用的联系人，保存所选项目。然而，实现这一点并不像我想象的那么简单。

我有以下代码，主要来自MSDN示例：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Navigation;
using Microsoft.Phone.Controls;
using Microsoft.Phone.Shell;
using Microsoft.Phone.UserData;
using System.Diagnostics;
namespace appNamespace
{
    public partial class contact : PhoneApplicationPage
    {
        public contact()
        {
            InitializeComponent();
        }
        private void showContacts(object sender, RoutedEventArgs e)
        {
            Contacts cons = new Contacts();
            //Identify the method that runs after the asynchronous search completes.
            cons.SearchCompleted += new EventHandler<ContactsSearchEventArgs>(Contacts_SearchCompleted);
            //Start the asynchronous search.
            cons.SearchAsync(String.Empty, FilterKind.None, "Contacts Test #1");
        }
        void Contacts_SearchCompleted(object sender, ContactsSearchEventArgs e)
        {
            //Do something with the results.
            MessageBox.Show(e.Results.Count().ToString());
            try
            {
                //Bind the results to the user interface.
                ContactResultsData.DataContext = e.Results;
            }
            catch (System.Exception)
            {
                //No results
            }
            if (ContactResultsData.Items.Any())
            {
                ContactResultsLabel.Text = "results";
            }
            else
            {
                ContactResultsLabel.Text = "no results";
            }
        }
        public void saveContacts(object sender, RoutedEventArgs e)
        {
            String strItem;
            foreach (Object selecteditem in ContactResultsData.SelectedItems)
            {
                MessageBox.Show(selecteditem.ToString());
                strItem = selecteditem as String;
                ContactResultsLabel.Text = strItem;
                System.Diagnostics.Debug.WriteLine(strItem);
                MessageBox.Show("Saving " + strItem);
            }
        }
    }
}

当在Lumia 920设备上运行代码时，该应用程序会显示联系人数量，但不会显示数据绑定列表。（请参阅下面的XAML）相反，应用程序会停止并引发异常（ApplicationException，调试器没有提供详细信息）

<phone:PhoneApplicationPage
    x:Class="appNamespace.contact"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"
    xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    FontFamily="{StaticResource PhoneFontFamilyNormal}"
    FontSize="{StaticResource PhoneFontSizeNormal}"
    Foreground="{StaticResource PhoneForegroundBrush}"
    SupportedOrientations="Portrait" Orientation="Portrait"
    mc:Ignorable="d"
    shell:SystemTray.IsVisible="True">
    <!--LayoutRoot is the root grid where all page content is placed-->
    <Grid x:Name="LayoutRoot" Background="Transparent">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <!--TitlePanel contains the name of the application and page title-->
        <StackPanel Grid.Row="0" Margin="12,17,0,28">
            <TextBlock Text="appName" Style="{StaticResource PhoneTextNormalStyle}"/>
            <TextBlock Text="contacts" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>
        </StackPanel>
        <!--ContentPanel - place additional content here-->
        <Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
            <StackPanel Height="Auto" Width="Auto" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Margin="0,0,0,10" >
                <TextBlock Name="ContactResultsLabel" Text="results are loading..." Style="{StaticResource PhoneTextLargeStyle}" TextWrapping="Wrap" />
                <ListBox Name="ContactResultsData" ItemsSource="{Binding}" Height="436" Margin="12,0" SelectionMode="Multiple" >
                    <ListBox.ItemTemplate>
                        <DataTemplate>
                            <TextBlock Name="ContactResults" Style="{StaticResource PhoneFontSizeMedium}" Text="{Binding Path=DisplayName, Mode=OneWay}" />
                        </DataTemplate>
                    </ListBox.ItemTemplate>
                </ListBox>
            </StackPanel>
            <Button x:Name="showButton" Content="Show Contacts" HorizontalAlignment="Left" VerticalAlignment="Top" Width="218" Height="90" Margin="0,531,0,0" Click="showContacts"/>
            <Button x:Name="saveButton" Content="Save Contacts" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="238,531,0,0" Width="218" Height="90"/>
        </Grid>
    </Grid>
</phone:PhoneApplicationPage>

真希望有人能帮忙，我不明白为什么会出现这种例外。非常感谢。

<TextBlock Name="ContactResults" Style="{StaticResource PhoneFontSizeMedium}" Text="{Binding Path=DisplayName, Mode=OneWay}" />

<TextBlock Name="ContactResults" FontSize="{StaticResource PhoneFontSizeMedium}" Text="{Binding Path=DisplayName, Mode=OneWay}" />