maui-theming

Design

Guide for theming .NET MAUI apps—light/dark mode support, AppThemeBinding, dynamic resources, ResourceDictionary theme switching, and system theme detection. USE FOR: "dark mode", "light mode", "theming", "AppThemeBinding", "theme switching", "ResourceDictionary theme", "dynamic resources", "system theme detection", "color scheme", "app theme". DO NOT USE FOR: localization or language switching (use maui-localization), accessibility visual adjustments (use maui-accessibility), or app icons (use maui-app-icons-splash).

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.NET MAUI Theming

Choosing your approach

Approach	Best for	Limitation
AppThemeBinding	Auto light/dark with OS — minimal code	Only two themes (light + dark)
ResourceDictionary swap	Custom branded themes, >2 themes, user preference	More setup, must use `DynamicResource` everywhere
Both combined	Auto OS response + custom theme colors	Most flexible but most complex

Critical gotchas

Android: ConfigChanges.UiMode is REQUIRED

MainActivity must include ConfigChanges.UiMode or theme change events will not fire and the activity restarts instead of handling the change:

[Activity(Theme = "@style/Maui.SplashTheme",
          MainLauncher = true,
          ConfigurationChanges = ConfigChanges.ScreenSize
                               | ConfigChanges.Orientation
                               | ConfigChanges.UiMode  // ← Required for theme detection
                               | ConfigChanges.ScreenLayout
                               | ConfigChanges.SmallestScreenSize
                               | ConfigChanges.Density)]
public class MainActivity : MauiAppCompatActivity { }

Without UiMode, toggling dark mode in Android settings causes a full activity restart — losing navigation state and appearing as a crash to users.

CSS themes cannot be swapped at runtime

MAUI supports CSS styling, but CSS-based themes cannot be swapped dynamically. Use ResourceDictionary theming for runtime switching.

DynamicResource vs StaticResource

When using ResourceDictionary theme switching, you must use DynamicResource:

<!-- ✅ Updates when theme dictionary changes -->
<Label TextColor="{DynamicResource PrimaryTextColor}" />

<!-- ❌ Frozen at first load — won't update on theme switch -->
<Label TextColor="{StaticResource PrimaryTextColor}" />

Quick reference

OS light/dark → AppThemeBinding markup extension
Theme colors in C# → SetAppThemeColor(), SetAppTheme<T>()
Read OS theme → Application.Current.RequestedTheme
Force theme → Application.Current.UserAppTheme = AppTheme.Dark
Theme changes → RequestedThemeChanged event
Custom switching → Swap ResourceDictionary in MergedDictionaries
Runtime bindings → DynamicResource (not StaticResource)