https://learn.microsoft.com/en-us/uwp/api/windows.ui.xaml.frameworkelement.requestedtheme?view=winrt-28000
FrameworkElement.RequestedTheme Property (Windows.UI.Xaml) - Windows apps | Microsoft Learn
Gets or sets the UI theme that is used by the UIElement (and its child elements) for resource determination. The UI theme you specify with RequestedTheme can...
propertywindowsuixamlapps