csharp

name	csharp
description	Use when: write or review modern, idiomatic C# with async, nullable reference types, and clean structure.

Goal: modern C# that is null-safe, async-correct, and testable.

Use for:

• new classes, services, or APIs in C#/.NET
• reviewing async usage, nullability, and structure
• modernizing legacy patterns to current language features

Workflow:

1. Enable nullable reference types and honor the warnings.
2. Use async/await end to end; never block on async code.
3. Model data with records and pattern matching.
4. Prefer immutable types and expression-bodied members.
5. Inject dependencies; program to interfaces, not concretions.
6. Verify with the test runner, analyzers, and dotnet format.

Idioms:

• records for value-like data
• LINQ for transformations over manual loops
• pattern matching and switch expressions
• using declarations for IDisposable
• CancellationToken threaded through async APIs

Rules:

• never call .Result/.Wait() on a Task; await it
• treat nullable warnings as errors to fix
• pass CancellationToken to cancellable operations
• keep methods small; depend on abstractions for testability