Use When

• Review, audit, or enforce .NET/C# coding standards
• Fix or clean up code quality issues in one or more C# files
• Apply best practices, prepare for PR/code review, or onboard a codebase
• Target a sub-skill area: documentation, architecture, DI, localization, async patterns, configuration, error handling, or code quality

See references/trigger-phrases.md for example trigger phrases per category.

Do Not Invoke For

• Non-C# / non-.NET codebases
• Read-only .NET questions — answer directly without running the full skill
• Trivial edits unrelated to standards (e.g. rename a variable, add a property)

Pre-Flight: Detect Target Framework

Before processing any files, inspect every *.csproj in the workspace:

• Read <LangVersion> and <TargetFramework> / <TargetFrameworks>.
• Record the minimum C# language version across all projects.
• Sub-skills that reference C# 10+ features (file-scoped namespaces), C# 11+ features (required keyword), C# 12+ features (collection expressions, primary constructors), C# 13+ features (params ReadOnlySpan<T>), or C# 14+ features (field keyword, extension member syntax) must only be applied when the detected language version supports them.
• Determine the set of target frameworks (e.g., net6.0, net7.0, net8.0, net8.0-*) across all projects, and identify the lowest target framework.
• Only apply .NET runtime–specific recommendations when the target frameworks support them:
  • Treat net8.0 and net8.0-* as supporting .NET 8 APIs (e.g., IExceptionHandler, Keyed DI services, IProblemDetailsService).
  • When all projects target only net6.0 / net7.0, do not recommend APIs that were introduced in .NET 8 or later; instead, prefer equivalent patterns compatible with those target frameworks.
  • For multi-targeted projects, default to guidance that is compatible with the lowest target framework unless the user explicitly requests advice for a newer target.

Scope

Analyze ${selection} if provided. If no selection is made, analyze ALL C# files (**/*.cs) in the workspace, excluding the files listed below.

Excluded Files

Skip files matching these patterns — applying fixes to generated or migrated code causes build failures:

• **/*.g.cs, **/*.Designer.cs — auto-generated source
• **/obj/**, **/bin/** — build output
• **/Migrations/** — EF Core migration files

Test projects (files under a project whose name contains Tests, Specs, or Test):

• Skip sub-skills 4 (Localization) — these produce noise in test code.
• Apply all remaining sub-skills normally.

Execution Rules

• Before applying each sub-skill, use the file reading tool to load the sub-skill file listed in the table below. Do not rely on memorised rules.
• Process every file in scope. Do not skip any.
• Execute each sub-skill below in order, sequentially, for every file.
• After completing all sub-skills, output a consolidated findings summary table grouped by file and sub-skill.
• For each finding, write the corrected code directly to the file using the file editing tools. Use // ...existing code... to preserve unchanged sections.
• APPLY ALL CHANGES after the summary table — do not stop at summarising. Every finding must result in an implemented edit.
• DO NOT STOP until every sub-skill has been applied to every file in scope and every finding has been fixed.
• If context limits are reached, emit a checkpoint summary listing:
  • Sub-skills completed
  • Files fully reviewed
  • Remaining files and sub-skills Then await the next prompt to continue from where you left off.

Sub-Skills (execute in order)

Consolidated Findings Summary Format

After all sub-skills are complete, produce a single Markdown table:

Severity: Critical = correctness/runtime risk · Warning = maintainability/perf · Info = style

Apply Findings

After outputting the summary table, apply findings in order:

1. Open the identified file.
2. Write the corrected code directly to the file.
3. Preserve all unchanged code using // ...existing code....
4. Confirm each applied fix with a ✅ checklist item.
5. Critical, Warning and Info findings must all be fixed.
6. Do not stop until all Critical, Warning and Info findings are written to disk.