Winui Code Review Agent Skill

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 into your build when you compile via the BuildAndRun.ps1 script that ships with that skill — the script drops a temporary Directory.Build.props into the project that loads the analyzer DLL and its .targets, then cleans up after the build. Plain dotnet build (or VS) does not load the analyzer automatically; if you want it to surface as build diagnostics outside the script, add the <Analyzer Include="..." /> and <Import Project="..." /> to your 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:

• Issues found: List each with file, line, and what's wrong
• Severity: Error (must fix), Warning (should fix), or Note (could improve)
• 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).