Dotnet Patterns

This is a comprehensive reference for writing production-quality C# code the way experienced .NET developers actually do it. It covers the patterns that matter: dependency injection with interfaces, async/await done right with CancellationToken threading, immutability with records, the options pattern for configuration, and proper repository implementations with EF Core. The examples are realistic, showing both good and bad approaches. Use this when you want Claude to write .NET code that follows modern conventions instead of generating the mutable-everything, sync-over-async antipatterns that plague a lot of codegen. The result pattern section alone is worth having loaded if you're tired of exception-driven control flow.

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last updated: Aug 21, 2026

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Install

$ npx -y skills add affaan-m/ecc --skill dotnet-patterns --agent claude-code

Installs into .claude/skills of the current project.

Files

.NET Development Patterns

Idiomatic C# and .NET patterns for building robust, performant, and maintainable applications.

When to Activate

Writing new C# code
Reviewing C# code
Refactoring existing .NET applications
Designing service architectures with ASP.NET Core

Core Principles

1. Prefer Immutability

Use records and init-only properties for data models. Mutability should be an explicit, justified choice.

// Good: Immutable value object
public sealed record Money(decimal Amount, string Currency);

// Good: Immutable DTO with init setters
public sealed class CreateOrderRequest
{
    public required string CustomerId { get; init; }
    public required IReadOnlyList<OrderItem> Items { get; init; }
}

// Bad: Mutable model with public setters
public class Order
{
    public string CustomerId { get; set; }
    public List<OrderItem> Items { get; set; }
}

2. Explicit Over Implicit

Be clear about nullability, access modifiers, and intent.

// Good: Explicit access modifiers and nullability
public sealed class UserService
{
    private readonly IUserRepository _repository;
    private readonly ILogger<UserService> _logger;

SKILL.md on GitHub