WPF - Override Inherited Style on child / inner controls

Question

So this particular answer seems to partially work: Reset inherited WPF style?

However, it doesn't seem to override styling on "inner" elements. For example, if I set the TextBlock Foreground to red in my main App.xaml file, it will change all TextBlock elements, but it will also impact controls that have inner/templated controls, like the text of a Button element.

When I try to override the style later, it impacts only the direct TextBlock elements. Buttons still seem to use the red text styling from the App.xaml.

In App.xaml:

<Application.Resources>
    <Style TargetType="{x:Type TextBlock}">
        <Setter Property="Foreground" Value="Red" />
    </Style>
</Application.Resources>

MainWindow.xaml contents (both controls show red text):

<StackPanel>
    <TextBlock>Hello World! I should be red!</TextBlock>
    <Button Click="Button_Click" Content="I'm red, too. Click me to open a new Popup!" />
</StackPanel>

The Button_Click event:

private void Button_Click(object sender, RoutedEventArgs e)
{
    var x = new Popup();
    x.Show();
}

And Popup.xaml:

<Window.Resources>
    <Style TargetType="{x:Type TextBlock}">
        <Setter Property="Foreground" Value="Blue" />
    </Style>
</Window.Resources>
<StackPanel>
    <TextBlock>Hello World, I'm blue!</TextBlock>
    <Button Content="Oh no! I should be blue, too, but I'm red!" />
</StackPanel>

The result:

How can I make the style within Popup.xaml have the same level of impact as the same style in App.xaml?

EDIT: I should note that the real underlying motivation here is that I build plugins for an enterprise app. The base app has a lot of styling that is carrying over into my plugins, and I'm trying to come up with a "reset all styles" resource dictionary, but when I have things like DataGrids, the content elements are not being reset - they're inheriting styles from the base app, and I'm trying to find an effective way of resetting them without being overly explicit.

Possible duplicate of Default TextBlock style overriding button text color — Neil B
Not really a duplicate. Similar, and has the same final answer, but the below answer with that article is much better. — jhilgeman

Neil B Neil B · Accepted Answer · 2019-04-04T15:35:08

I think this article explains what you are experiencing, and why the style inheritance takes a different precedence than you expect.

Here you can find the info about dependency property precedence.

As far as I know the only way to keep a general style like this from affecting sub elements is to explicitly style them. (Not a good approach)

WPF - Override Inherited Style on child / inner controls

1 Answers