WPF——TargetNullValue(如何在绑定空值显示默认字符)

说明：在数据绑定时，如果有些字段为空值，那么在数据绑定时可以用默认值来显示为空的字段。

 <Grid>
        <ListBox x:Name="lstPeople" Width="400">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <StackPanel Orientation="Horizontal">
                        <TextBlock Text="{Binding Path=FirstName}" />
                        <TextBlock Text=" " />
                        <TextBlock Text="{Binding LastName}" />
                        <TextBlock Text=", " />
                        <TextBlock Text="{Binding Age, TargetNullValue='Age Unknown'}" />
                    </StackPanel>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
    </Grid>

 public partial class MainWindow : Window
    {
        List<Person> lst;

        public MainWindow()
        {
            InitializeComponent();
            lst = new List<Person>();
            lst.Add(new Person() {FirstName="John", LastName="Doe", Age=34});
            lst.Add(new Person() { FirstName = "Jane", LastName = "Doe" });
            lst.Add(new Person() { FirstName = "Jack", LastName = "Frost", Age = 300 });
        }

        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            lstPeople.ItemsSource = lst;
        }
    }

    public class Person
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public int? Age { get; set; }
    }