author-component

# Author Blazor Component ## Core Rules - Data flows **down** via `[Parameter]`. Events flow **up** via `EventCallback<T>` (never `Action`/`Func`). - Never mutate `[Parameter]` properties. Copy to a private field in `OnParametersSet`. - Use `[Parameter] public T Prop { get; set; }` — never `required` or `init` (causes BL0007). - Use `[EditorRequired]` for required parameters. - Handle all states: loading, empty, loaded, error — each with `@if`/`@else`. - Use `@key` on repeated elements in loops for efficient diffing. - Use `IReadOnlyList<T>` (not `IEnumerable<T>`) for collection parameters. ## RenderFragment & Generics ```csharp [Parameter] public RenderFragment? ChildContent { get; set; } [Parameter] public RenderFragment<TItem>? RowTemplate { get; set; } // generic template ``` Use `@typeparam TItem` for generic components. ## File Patterns - **Single-file:** `.razor` with `@code` block when logic < ~50 lines. - **Code-behind:** `.razor` + `.razor.cs` with `partial class` when logic > ~50 lines. ## Disposal Implement `IAsyncDisposable` (not `IDisposable`) when the component owns subscriptions, timers, or CTS. In `DisposeAsync`: unsubscribe (`-=`), cancel CTS, dispose resources. Never call `StateHasChanged`. ## Async Patterns - `await` every async operation. Never use `.Result`, `.Wait()`, `Task.Run`, `ContinueWith`, `Thread.Start`. - **Debounce:** `Task.Delay` + `CancellationTokenSource`. Cancel old CTS, create new, await delay, do work. Never use `System.Threading.Timer` or `System.Timers.Timer`. - **Polling:** Loop in `OnInitializedAsync` with `await Task.Delay(interval, token)` — stays on sync context. - **External events** (`Action<T>`): Use `async void` handler + `await InvokeAsync(() => { state++; StateHasChanged(); })` + `catch` → `DispatchExceptionAsync`. Never `_ = InvokeAsync(...)`. - Cancel CTS in `DisposeAsync`. Don't catch `ObjectDisposedException` — use CTS cancellation. ## Don'ts - `required`/`init` on `[Parameter]` — runtime failure - Mutate `[Parameter]` — copy to private field in `OnParametersSet` - `Action`/`Func` for events — use `EventCallback<T>` - `Task.Run`/`.Result`/`.Wait()`/Timer for debounce — deadlock or thread-pool escape - Inline `style` attributes — use CSS classes or `data-*` attributes - `catch { throw; }` — use `when` guard or let exceptions propagate - Gold-plating: ARIA, wrapper divs, accessibility features not requested - `_ = InvokeAsync(...)` — swallows exceptions; use `async void` + `DispatchExceptionAsync`