Scans .NET code for ~50 performance anti-patterns across async, memory, strings, collections, LINQ, regex, serialization, and I/O with tiered severity classification. Use when analyzing .NET code for optimization opportunities, reviewing hot paths, or auditing allocation-heavy patterns.
Create ASP.NET Minimal API endpoints with proper OpenAPI documentation
Get best practices for C# async programming
Ensure that C# types are documented with XML comments and follow best practices for documentation.
Performs safe, behavior-preserving refactoring of C#/.NET code, verified with build, tests, and analyzers. USE FOR: rename or move a symbol/type/file; extract a method/type/interface; inline a wrapper/method/local; merge or consolidate near-identical classes or duplicate helpers; split or modernize C# code; generated/partial declarations; public, serialized, friend-assembly, or multi-targeted contracts; and mixed requests where a feature, bug fix, package/framework upgrade, public nullability change, or other behavior/contract change is presented as a refactor and must be separated or declined. DO NOT USE FOR: ordinary feature or bug-fix requests not framed as refactoring; upgrades after reclassification (use dotnet-upgrade); new tests; or formatting-only passes (use dotnet format).
C# and .NET testing patterns with xUnit, FluentAssertions, mocking, integration tests, and test organization best practices. Use when writing or reviewing xUnit tests, mocks, or integration tests in a C# / .NET project.
Get best practices for XUnit unit testing, including data-driven tests
Master C#/.NET backend development patterns for building robust APIs, MCP servers, and enterprise applications. Covers async/await, dependency injection, Entity Framework Core, Dapper, configuration, caching, and testing with xUnit. Use when developing .NET backends, reviewing C# code, or designing API architectures.
Ensure .NET/C# code meets best practices for the solution/project.
Review the C#/.NET code for design pattern implementation and suggest improvements.
Idiomatic C# and .NET patterns, conventions, dependency injection, async/await, and best practices for building robust, maintainable .NET applications. Use when writing or reviewing C# / .NET code — DI, async, or general conventions.
.NET timezone handling guidance for C# applications. Use when working with TimeZoneInfo, DateTimeOffset, NodaTime, UTC conversion, daylight saving time, scheduling across timezones, cross-platform Windows/IANA timezone IDs, or when a .NET user needs the timezone for a city, address, region, or country and copy-paste-ready C# code.
Guide developers through capturing diagnostic artifacts to diagnose production .NET performance issues. Use when the user needs help choosing diagnostic tools, collecting performance data, or understanding tool trade-offs across different environments (Windows/Linux, .NET Framework/modern .NET, container/non-container).
Guides creation and modification of ASP.NET Core Web API endpoints with correct HTTP semantics, OpenAPI metadata, and error handling. USE FOR: adding new API endpoints (controllers or minimal APIs), wiring up OpenAPI/Swagger, creating .http test files, setting up global error handling middleware. DO NOT USE FOR: general C# coding style, EF Core data access or query optimization (use optimizing-ef-core-queries), frontend/Blazor work, gRPC services, or SignalR hubs.
ALWAYS USE before running .NET tests or answering with a test command or flags. Trigger on "run the tests", "exact dotnet test command", one test/class/category/trait/target framework, combined filters, --filter-query, --no-build, --diag, diagnostic logs, TRX, coverage collection, crash/hang dumps, filter errors, or unrecognized options. Chooses repository-compatible classic, VSTest, bridged MTP, or native MTP syntax for MSTest/xUnit/NUnit/TUnit. DO NOT USE for platform identification alone (platform-detection), writing or debugging test code, interpreting an existing coverage report, CI investigation, migration, or a persistent hot reload/watch loop.