Wpf – DialogResult WPF

I am reading one book which says

Rather than setting the DialogResult
by hand after the user clicks a
button, you can designate a button as
the accept button (by setting
IsDefault to true). Clicking that
button automatically sets the
DialogResult of the window to true.
Similarly, you can designate a button
as the cancel button (by setting
IsCancel to true), in which case
clicking it will set the DialogResult
to Cancel.

This is the MainWindow:

<Window x:Class="WpfApplicationWPF.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Width="400" Height="400">
    <StackPanel>

        <Button Name="BtnShowDialogStatus" Click="BtnShowDialogStatus_Click">DIALOG RESULT</Button>
    </StackPanel>
</Window>

Code for click event:

private void BtnShowDialogStatus_Click(object sender, RoutedEventArgs e)
{
    MessageBox.Show(new NewWindow().ShowDialog().ToString());
}

And this is the Dialog box which I am opening on the click event:

<Window x:Class="WpfApplicationWPF.NewWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="NewWindow" Height="300" Width="300">
    <StackPanel>
        <Button Name="BtnDEfault" IsDefault="True" Click="BtnDEfault_Click">DEFAULT BUTTON</Button>
        <Button Name="BtnCancel" IsCancel="True" Click="BtnCancel_Click">CANCEL BUTTON</Button>
    </StackPanel>
</Window>   

This is the code for it:

private void BtnDEfault_Click(object sender, RoutedEventArgs e)
{
    this.Close();
}

private void BtnCancel_Click(object sender, RoutedEventArgs e)
{
    this.Close();
}

I can see it returning the DialogResult only as false no matter I click the default or cancel button.