Theming

WinUI 3 supports tri-state theming: Light, Dark, and High Contrast.

• Set app-level theme via Application.RequestedTheme, override per-element with FrameworkElement.RequestedTheme
• Colors and brushes MUST use ThemeResource (not StaticResource) — enables runtime theme switching
• Semantic color resources (TextFillColorPrimary, CardBackgroundFillColorDefault) SHOULD be used instead of hex values
• Define custom theme-aware colors in a ResourceDictionary with Default/Light/Dark theme dictionaries

<!-- Good: semantic theme resource -->
<TextBlock Foreground="{ThemeResource TextFillColorPrimaryBrush}" />

<!-- Bad: hard-coded color -->
<TextBlock Foreground="#FFFFFF" />

Change History