wpf中元素的Visibility和IsVisible出现矛盾的情况

ui

<StackPanel Margin="5">
        <Border x:Name="bd1">
            <TextBlock Name="tb1" Text="123" />
        </Border>
        <Button
            x:Name="btn1"
            Click="btn1_Click"
            Content="隐藏Border" />
    </StackPanel>

后台代码

private void btn1_Click(object sender, RoutedEventArgs e)
{
    bd1.Visibility = Visibility.Hidden;
    Console.WriteLine(tb1.Visibility); //Visible
    Console.WriteLine(tb1.IsVisible); //False
}