antigravity-skills-reference/skills/avalonia-zafiro-development/avalonia-reactive-rules.md

Avalonia, Zafiro & Reactive Rules

Avalonia UI Rules

• Strict Avalonia: Never use System.Drawing; always use Avalonia types.
• Pure ViewModels: ViewModels must never reference Avalonia types.
• Bindings Over Code-Behind: Logic should be driven by bindings.
• DataTemplates: Prefer explicit DataTemplates and typed DataContexts.
• VisualStates: Avoid using VisualStates unless absolutely required.

Zafiro Guidelines

• Prefer Abstractions: Always look for existing Zafiro helpers, extension methods, and abstractions before re-implementing logic.
• Validation: Use Zafiro's ValidationRule and validation extensions instead of ad-hoc reactive logic.

DynamicData & Reactive Rules

The Mandatory Approach

• Operator Preference: Always prefer DynamicData operators (Connect, Filter, Transform, Sort, Bind, DisposeMany) over plain Rx operators when working with collections.
• Readable Pipelines: Build and maintain pipelines as a single, readable chain.
• Lifecycle: Use DisposeWith for lifecycle management.
• Minimal Subscriptions: Subscriptions should be minimal, centralized, and strictly for side-effects.

Forbidden Anti-Patterns

• Ad-hoc Sources: Do NOT create new SourceList / SourceCache on the fly for local problems.
• Logic in Subscribe: Do NOT place business logic inside Subscribe.
• Operator Mismatch: Do NOT use System.Reactive operators if a DynamicData equivalent exists.

Canonical Patterns

Validation of Dynamic Collections:

this.ValidationRule(
        StagesSource
            .Connect()
            .FilterOnObservable(stage => stage.IsValid)
            .IsEmpty(),
        b => !b,
        _ => "Stages are not valid")
    .DisposeWith(Disposables);

Filtering Nulls: Use WhereNotNull() in reactive pipelines.

this.WhenAnyValue(x => x.DurationPreset).WhereNotNull()