MAUI Localization and Theming

Use this skill when a MAUI app needs translated strings, culture-specific formatting, right-to-left support, or runtime theme changes.

Workflow

1. Inspect existing Resources, ResourceDictionary, App.xaml, and platform language declarations.
2. Put user-visible strings in RESX resources or the app's existing localization service.
3. Use culture-aware formatting for dates, numbers, and currency.
4. If runtime language switching is required, centralize culture updates and notify UI bindings.
5. Add RTL support through FlowDirection and test with an RTL culture.
6. Define colors, spacing, and styles as resources.
7. Use AppThemeBinding for simple light/dark values and DynamicResource for values that change at runtime.
8. Set Application.Current.UserAppTheme only when the user explicitly chooses a theme; use Unspecified for system theme.

RESX Pattern

Use a default resource file plus culture-specific files:

Resources/Strings/AppResources.resx
Resources/Strings/AppResources.es.resx
Resources/Strings/AppResources.fr.resx

Reference generated resources from XAML or ViewModels instead of hard-coded strings. Keep resource keys stable and descriptive.

Runtime Culture Switching

When the user changes language:

• Set CultureInfo.DefaultThreadCurrentCulture.
• Set CultureInfo.DefaultThreadCurrentUICulture.
• Update any generated resource culture property if the app uses one.
• Notify bound localized strings, recreate affected pages, or use a localization manager that raises change notifications.
• Persist the selected culture in Preferences only after the user chooses it.

Do not assume changing the thread culture automatically refreshes every existing binding. Existing pages usually need notification or recreation.

Platform Language Declarations

RTL Guidance

• Use FlowDirection="MatchParent" for most pages and layouts.
• Set FlowDirection="RightToLeft" only when forcing a specific surface.
• Avoid left/right naming in resources; prefer start/end semantics in code and design tokens.
• Verify icons and gestures that imply direction.

Theme Patterns

<ContentPage BackgroundColor="{AppThemeBinding Light=#FFFFFF, Dark=#111111}" />

<Label TextColor="{DynamicResource PrimaryTextColor}" />

Runtime theme changes should update resource dictionaries or Application.Current.UserAppTheme:

Application.Current!.UserAppTheme = AppTheme.Dark;

Use DynamicResource for resources that must react after the page is created. Use StaticResource only when values are not expected to change at runtime.

Validation Checklist

• User-visible strings are resource-backed.
• Culture changes update existing UI or intentionally recreate affected pages.
• RTL cultures have been considered for layout direction and icons.
• Theme resources use AppThemeBinding or DynamicResource appropriately.
• User theme selection can return to system default.