maui-performance（毛伊岛表演）

.NET MAUI Performance Optimization

Profiling

• dotnet-trace: Cross-platform profiler for all MAUI targets. Collect traces with: dotnet-trace collect --process-id <PID> --providers Microsoft-DotNETCore-SampleProfiler
• PerfView (Windows only): Use for deep allocation and CPU analysis on WinUI targets.
• Profile before optimizing — measure, don't guess.

Compiled Bindings

• Always set x:DataType on pages/views to enable compiled bindings.
• Compiled bindings are 8–20× faster than reflection-based bindings.
• Required for NativeAOT and full trimming — reflection bindings break under trimming.
• Apply x:DataType at the highest reasonable scope (page or root element).

<ContentPage xmlns:vm="clr-namespace:MyApp.ViewModels"
             x:DataType="vm:MainViewModel">
    <Label Text="{Binding Title}" />
</ContentPage>

• For DataTemplate inside CollectionView/ListView, set x:DataType on the template root:

<DataTemplate x:DataType="model:Item">
    <Label Text="{Binding Name}" />
</DataTemplate>

• Minimize unnecessary bindings: Static content that never changes doesn't need {Binding}. Use literal values or x:Static instead.

Layout Optimization

• Avoid nested single-child layouts — a StackLayout with one child is pointless overhead.
• Prefer Grid over nested StackLayout/VerticalStackLayout — Grid resolves layout in a single pass.
• Use IsVisible="False" to hide elements rather than adding/removing from the tree at runtime.
• Remove unnecessary wrapper containers — every layout adds a measure/arrange pass.
• Avoid AbsoluteLayout when Grid with row/column definitions achieves the same result.
• Set explicit WidthRequest/HeightRequest where sizes are known to reduce measure passes.

CollectionView and ListView

• Use ItemSizingStrategy="MeasureFirstItem" on CollectionView when items have uniform height — avoids measuring every item individually.

<CollectionView ItemSizingStrategy="MeasureFirstItem"
                ItemsSource="{Binding Items}">

• Prefer CollectionView over ListView for new development.
• Keep DataTemplate visual trees shallow — fewer nested layouts per item.

Image Optimization

• Size images to display resolution — don't load a 4000×3000 image for a 200×200 display.
• Use Aspect="AspectFill" or AspectFit and set explicit dimensions.
• Cache downloaded images: CachingEnabled="True" (default) on UriImageSource, set CacheValidity.
• Use platform-appropriate formats (WebP for Android, HEIF/PNG for iOS).
• For icons and simple graphics, prefer SVG or vector-based font icons.

Resource Dictionaries

• App-level (App.xaml): Shared styles, colors, converters used across multiple pages.
• Page-level: Styles/resources specific to a single page — keeps App.xaml lean.
• Avoid duplicating resources across dictionaries.
• Use MergedDictionaries to organize large resource sets without bloating a single file.

Startup Optimization

• Minimize work in App constructor and MainPage constructor.
• Defer non-essential service registration — use lazy initialization where possible.
• Reduce the number of XAML pages parsed at startup (use Shell routing for deferred loading).
• Remove unused Handlers/Effects registrations from MauiProgram.cs.
• On Android, ensure AndroidManifest.xml doesn't force unnecessary permissions checks at launch.

Trimming

Enable IL trimming to reduce app size and remove unused code:

<PropertyGroup>
    <PublishTrimmed>true</PublishTrimmed>
    <TrimMode>full</TrimMode>
</PropertyGroup>

• Test thoroughly — trimming can remove code accessed only via reflection.
• Use [DynamicDependency] or [UnconditionalSuppressMessage] to preserve reflection targets.
• Compiled bindings are essential — reflection-based bindings will be trimmed away.

NativeAOT

• NativeAOT compiles to native code ahead-of-time for faster startup and smaller footprint.
• Requirements: compiled bindings, no unconstrained reflection, trimming-compatible code.

<PropertyGroup>
    <PublishAot>true</PublishAot>
    <PublishTrimmed>true</PublishTrimmed>
</PropertyGroup>

• Audit third-party NuGet packages for trimming/AOT compatibility.
• Use [JsonSerializable] source generators instead of reflection-based JSON serialization.
• Run dotnet publish with AOT to verify no warnings before shipping.

Quick Checklist

1. ✅ x:DataType on all pages, templates, and data-bound views
2. ✅ No nested single-child layouts
3. ✅ Grid preferred over nested StackLayouts
4. ✅ Images sized to display, caching enabled
5. ✅ ItemSizingStrategy="MeasureFirstItem" on uniform CollectionViews
6. ✅ Startup work minimized and deferred
7. ✅ Trimming enabled and tested
8. ✅ Profile with dotnet-trace before and after changes