如何在WPF中数据绑定聚合函数(如sum)？

// ViewModel或者Code-behind中的代码
public class MyViewModel : INotifyPropertyChanged
{
    private ObservableCollection<int> numbers;
    private int sum;

    public MyViewModel()
    {
        numbers = new ObservableCollection<int>();
        numbers.CollectionChanged += Numbers_CollectionChanged;
    }

    public ObservableCollection<int> Numbers
    {
        get { return numbers; }
        set
        {
            numbers = value;
            OnPropertyChanged(nameof(Numbers));
        }
    }

    public int Sum
    {
        get { return sum; }
        set
        {
            sum = value;
            OnPropertyChanged(nameof(Sum));
        }
    }

    private void Numbers_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        // 计算聚合函数的结果
        Sum = Numbers.Sum();
    }

    // 实现INotifyPropertyChanged接口的代码
    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

<!-- XAML中的代码 -->
<Window.DataContext>
    <local:MyViewModel />
</Window.DataContext>

<Grid>
    <ItemsControl ItemsSource="{Binding Numbers}">
        <ItemsControl.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding}" />
            </DataTemplate>
        </ItemsControl.ItemTemplate>
    </ItemsControl>

    <TextBlock Text="{Binding Sum}" />
</Grid>