Semantic Pattern Authoring

Use when

• A recurring migrated page shape needs a post-transform rewrite.
• The change should stay in src/BlazorWebFormsComponents.Cli/SemanticPatterns/.
• You need targeted tests instead of broad pipeline edits.

Pattern

1. Match on post-transform markup/code-behind, not original Web Forms syntax.
2. Keep wrapper extraction and markup surgery in subsystem-local helpers.
3. Preserve explicit TODO markers for app-specific behavior that the CLI cannot safely infer.
4. Prefer compile-safe SSR output over preserving non-runnable validator/postback trees.
5. Add isolated tests that assert both pattern IDs and rewritten markup shape.
6. For query-bound data pages, prefer SelectMethod → SelectItems scaffolds plus [SupplyParameterFromQuery] / [Parameter] component properties when the original Web Forms method relied on model-binding attributes.
7. For blank action pages, generate an SSR handler scaffold (NavigationManager, query-bound properties, redirect target, OnParametersSet TODO) instead of leaving inert migrated HTML.

Current examples

• pattern-query-details — rewrites query-string / route-data SelectMethod pages to query-bound SelectItems stubs with TODO(bwfc-query-details).
• pattern-action-pages — rewrites action-only redirect pages to SSR handler scaffolds with TODO(bwfc-action-pages).