dotnet-csharp

name	dotnet-csharp
description	Baseline C# skill loaded for every .NET code path. Guides language patterns (records, pattern matching, primary constructors, C# 8-15), coding standards, async/await, DI, LINQ, serialization, domain modeling, concurrency, Roslyn analyzers, globalization, native interop (P/Invoke, LibraryImport, ComWrappers), WASM interop (JSImport/JSExport), and type design. Spans 25 topics. Do not use for ASP.NET endpoint architecture, UI framework patterns, or CI/CD guidance.
license	MIT
user-invocable	false

dotnet-csharp

Overview

C# language patterns, coding standards, and .NET runtime features for idiomatic, performant code. This consolidated skill spans 25 topic areas. Load the appropriate companion file from references/ based on the routing table below.

Always-Load Baseline

These references define correctness and quality standards that apply to all C# code — load them by default whenever producing or reviewing code, regardless of what the user asked for:

• references/coding-standards.md — naming conventions, file layout, style rules
• references/async-patterns.md — async/await correctness, ConfigureAwait, cancellation propagation (nearly all .NET code uses async)
• references/solid-principles.md — SOLID, DRY, single responsibility, dependency inversion, anti-pattern detection
• references/code-smells.md — common mistakes the agent should avoid without being told (async void, DI lifetime misuse, swallowed exceptions)
• references/dotnet-releases.md — .NET 10/11 and C# 14/15 features, version matrix, TFM-specific code generation rules (compensates for training data cutoff)

On-Demand References

Load these when the topic matches (see Routing Table keywords):

Routing Table

Topic	Keywords	Description	Companion File
Coding standards	naming, file layout, style rules	Baseline C# conventions (naming, layout, style rules)	references/coding-standards.md
Async/await	async, Task, ConfigureAwait, cancellation	async/await, Task patterns, ConfigureAwait, cancellation	references/async-patterns.md
Dependency injection	DI, services, scopes, keyed, lifetimes	MS DI, keyed services, scopes, decoration, lifetimes	references/dependency-injection.md
Configuration	Options pattern, user secrets, feature flags	Options pattern, user secrets, feature flags, IOptions<T>	references/configuration.md
Source generators	IIncrementalGenerator, GeneratedRegex, LoggerMessage	IIncrementalGenerator, GeneratedRegex, LoggerMessage, STJ	references/source-generators.md
Nullable reference types	annotations, migration, agent mistakes	Annotation strategies, migration, agent mistakes	references/nullable-reference-types.md
Serialization	System.Text.Json, Protobuf, MessagePack, AOT	System.Text.Json source generators, Protobuf, MessagePack	references/serialization.md
Channels	Channel<T>, bounded/unbounded, backpressure	Channel<T>, bounded/unbounded, backpressure, drain	references/channels.md
LINQ optimization	IQueryable vs IEnumerable, compiled queries	IQueryable vs IEnumerable, compiled queries, allocations	references/linq-optimization.md
Domain modeling	aggregates, value objects, domain events	Aggregates, value objects, domain events, repositories	references/domain-modeling.md
SOLID principles	SRP, DRY, anti-patterns, compliance checks	SOLID and DRY principles, C# anti-patterns, fixes	references/solid-principles.md
Concurrency	lock, SemaphoreSlim, Interlocked, concurrent collections	lock, SemaphoreSlim, Interlocked, concurrent collections	references/concurrency-patterns.md
Roslyn analyzers	DiagnosticAnalyzer, CodeFixProvider, multi-version	DiagnosticAnalyzer, CodeFixProvider, CodeRefactoring

Scope

• C# language features (C# 8-15)
• .NET runtime patterns (async, DI, config, serialization, channels, LINQ)
• Code quality (analyzers, editorconfig, code smells, SOLID)
• Type design and domain modeling
• File I/O and native interop
• Globalization (string comparison, CultureInfo, time zones, character processing, encoding)
• Input validation at the model level (DataAnnotations, IValidatableObject, FluentValidation, Options validation)

Out of scope

• ASP.NET Core / web API patterns (request-level validation, endpoint filters) -> dotnet-api
• UI framework patterns -> dotnet-ui
• Testing patterns -> dotnet-testing
• Build/MSBuild/project setup -> dotnet-tooling
• Performance profiling tools -> dotnet-tooling