按钮内容不会实时更改

我有一个按钮。我希望它是一个喜欢的切换按钮在一个列表框。参见下面的代码:

<Page
    x:Class="W.Pages.ExPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:Workout_EF.Pages"
    xmlns:converter="using:W.Converters"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:data="using:W.Model"
    mc:Ignorable="d">
    <Page.Resources>
        <converter:FavoriteValueConverter x:Key="favoriteConverter" />
    </Page.Resources>
    <Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
        <ListBox Name="MyListbox"
            SelectionMode="Single"                           
            ItemsSource="{x:Bind exs}"
            SelectionChanged="MyListbox_SelectionChanged">
            <ListBox.ItemTemplate>
                <DataTemplate x:DataType="data:Ex">
                    <StackPanel Orientation="Horizontal">
                        <Button Name="IsFavoriteToggle" Click="IsFavoriteToggle_Click">
                            <Button.Content>
                                <TextBlock
                                    x:Name="isFavoriteTextBlock" 
                                    Text="{x:Bind IsFavorite, Converter={StaticResource favoriteConverter}}"
                                    FontFamily="Segoe MDL2 Assets"/>
                            </Button.Content>
                        </Button>
                        <TextBlock 
                            VerticalAlignment="Center" 
                            FontSize="16" 
                            Text="{Binding ExName}"
                            Margin="20,0,0,0" />
                    </StackPanel>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
    </Grid>
</Page>

我的问题是，当我点击这个按钮，它不改变它的图标(从空星到全星，反之亦然)在实时。

如果列表框将再次加载，则显示正确的图标。

后面的代码是:

namespace W.Pages
{
    /// <summary>
    /// An empty page that can be used on its own or navigated to within a Frame.
    /// </summary>
    public sealed partial class ExPage : Page
    {
        ObservableCollection<Exs> exs = new ObservableCollection<Exs>();        
        public ExPage()
        {
            this.InitializeComponent();
        }
        protected override void OnNavigatedTo(NavigationEventArgs e)
        {
            List<Exs> tmpEx = e.Parameter as List<Exs>;
            foreach (Exs item in tmpEx)
            {
                exs.Add(item);
            }            
        }
        private void IsFavoriteToggle_Click(object sender, RoutedEventArgs e)
        {              
            Button button = sender as Button;
            int index = MyListbox.Items.IndexOf(button.DataContext);            
            Ex ex = (Exs)MyListbox.Items[index];
            DAL.SetToFavorite(ex, !ex.IsFavorite);
        }
    }
}

我注意到itemsource可能有一些问题。它需要在点击按钮后更改其内容。