ListView和TextBox，x:Null

<Window x:Class="WpfApp_Delete.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525"
        xmlns:Custom="clr-namespace:WpfApp_Delete"
        >
    <Window.Resources>
        <Custom:DemoList x:Key="MyList">
            <Custom:Demo Address="黄石" Sex="男" />
            <Custom:Demo Address="铁山" Sex="女"/>
        </Custom:DemoList>
        <Custom:Demo x:Key="MyDemo" Address="黄石" Sex="男" />
    </Window.Resources>
    <Grid DataContext="{StaticResource MyList}">
        <Grid.Resources>
            <!--x:Null的事例-->
            <Style TargetType="Button">
                <Setter Property="Width" Value="200"/>
            </Style>
            <Style TargetType="ListViewItem">
                <Setter Property="HorizontalContentAlignment" Value="Center"/>
            </Style>
        </Grid.Resources>
        <TextBox Height="23" HorizontalAlignment="Left" Margin="10,10,0,0" Name="textBox1" Text="{Binding ElementName=lvRoot, Path=SelectedItem.Sex}" VerticalAlignment="Top" Width="120" />
        <ListView Name="lvRoot" Height="100" HorizontalAlignment="Left" Margin="10,43,0,0" VerticalAlignment="Top" Width="481" ItemsSource="{Binding}" >
            <ListView.View>
                <GridView>
                    <GridViewColumn DisplayMemberBinding="{Binding Address}" Header="住址" Width="100"/>
                    <GridViewColumn DisplayMemberBinding="{Binding Sex}" Header="性别" Width="100"/>
                </GridView>
            </ListView.View>
        </ListView>
        <!--x:Null的事例-->
        <Button Content="Button" Height="23" HorizontalAlignment="Left" Margin="35,157,0,0" Name="button1" VerticalAlignment="Top" />
        <Button Content="Button" Height="23" HorizontalAlignment="Left" Margin="265,157,0,0" Name="button2" Style="{x:Null}" VerticalAlignment="Top" />
    </Grid>
</Window>