Winui Code Review

When to Use

Run a code review after the app builds and before committing. This catches quality issues that aren't build errors and aren't visible in UI tests — patterns that compile and run but are wrong, fragile, or slow.

How to Review

Read through the project's XAML and C# files and check each section below. The Microsoft.WindowsAppSDK.Analyzers Roslyn analyzer ships with the winui-dev-workflow skill and is injected when BuildAndRun.ps1 calls project-mode winapp run. The wrapper supplies a temporary file through the environment-backed MSBuild CustomAfterDirectoryBuildProps hook, preserving SDK composition and each project's normal Directory.Build.props discovery (including referenced projects), then restores the environment and removes the temporary file. Plain winapp run, dotnet build, and Visual Studio do not load the analyzer automatically; to enable it outside the wrapper, add the <Analyzer Include="..." /> and <Import Project="..." /> entries to the project's own Directory.Build.props (or wait for the planned NuGet package).

The analyzer catches a curated set of WinUI 3 / Windows App SDK issues with categorized 4-digit IDs:

• WUI0xxx — UWP → WinUI 3 API compatibility (UwpXamlNamespace, Window.Current, CoreDispatcher, GetForCurrentView)
• WUI1xxx — Migration-table data-driven hints (UWP API has WinAppSDK equivalent, no equivalent, feature-area hint)
• WUI2xxx — Runtime / layout / XAML pitfalls (raw TabView content, nested x:Bind without fallback, x:Bind without Mode, null Converter, missing AutomationId, attached-property syntax)
• WUI3xxx — MVVM patterns (old [ObservableProperty] field syntax)
• WUI4xxx — Interop (WebView2 not initialized, removed ONNX Runtime GenAI APIs WUI4101-WUI4103)

Every diagnostic ships at Warning severity (no rule is Error) and includes a helpLinkUri. Suppress noise with #pragma warning disable WUIxxxx or <NoWarn> as usual — the analyzer's SuppressionTests verify that pragma suppression round-trips correctly.

MVVM Compliance

• ViewModels extend ObservableObject, use [ObservableProperty] partial properties (not fields)
• Commands use [RelayCommand] attribute, not manual ICommand implementations
• No UI types in ViewModels (SolidColorBrush, Visibility, BitmapImage) — these belong in converters or XAML
• No business logic in code-behind — only navigation, dialog coordination, and event wiring
• async Task for async methods, async void only for event handlers
• Never replace ObservableCollection<T> — use .Clear() + re-add

x:Bind and Data Binding

• All bindings use {x:Bind}, not {Binding}
• Mode=OneWay or TwoWay set explicitly — OneTime default causes blank UI for dynamic data
• x:DataType set on every DataTemplate — required for compiled x:Bind
• No nested nullable paths (e.g., ViewModel.Selected.Name) without FallbackValue
• Command bindings can use OneTime (commands don't change) — don't add Mode=OneWay to Command="{x:Bind}"

Accessibility

• AutomationProperties.AutomationId on every interactive control (Button, TextBox, ComboBox, ToggleSwitch, ListView, NavigationViewItem)
• AutomationProperties.Name on icon-only buttons and controls without visible text
• Semantic controls (Button, HyperlinkButton) — not clickable Border/TextBlock
• No information conveyed by color alone

Theming

• All colors use {ThemeResource} brushes — no hardcoded #FF0000 or Color="Blue"
• Typography uses built-in styles (TitleTextBlockStyle, SubtitleTextBlockStyle, BodyTextBlockStyle, CaptionTextBlockStyle) — no raw FontSize
• Spacing uses 4px grid multiples (4, 8, 12, 16, 24, 32, 48)
• Corner radius uses ControlCornerRadius / OverlayCornerRadius — not hardcoded values
• Styles referenced with {StaticResource} not {ThemeResource} (except for brush usage sites)

Security

• No secrets, API keys, or tokens in source code
• No Process.Start with unsanitized user input
• External input validated and sanitized before use
• File paths from user input not used directly in File.Delete / File.WriteAllText without validation

Performance

• Long or dynamic lists use ListView/GridView (virtualized), not StackPanel with foreach
• x:Load for content that's not always visible (e.g., dialogs, secondary panels)
• Heavy work off UI thread via Task.Run or async/await — never block UI
• No .Result / .Wait() / .GetAwaiter().GetResult() — these deadlock the UI thread
• using statements on all disposable objects (Model, Tokenizer, InferenceSession, Generator)

Globalization

• User-facing strings use x:Uid in XAML and ResourceLoader in C# — not hardcoded
• String resources in Strings/en-us/Resources.resw (not .resx)
• Date/number formatting uses CultureInfo.CurrentCulture — not hardcoded formats
• Layout supports RTL (FlowDirection inherited from root, no absolute positioning that breaks in RTL)
• No string concatenation for user-facing messages — use string.Format or interpolation with resource strings

Review Report

After reviewing, summarize:

1. Issues found: List each with file, line, and what's wrong
2. Severity: Error (must fix), Warning (should fix), or Note (could improve)
3. Suggested fixes: Specific code changes for each issue

References

For detailed rules with code examples, see references/quality-rules.md — covers performance deep dives (x:Phase, layout optimization), security (PasswordVault, DPAPI, WebView2 hardening), accessibility (keyboard nav, screen readers), code quality (.editorconfig, naming), and globalization (x:Uid patterns, RTL, pluralization).