dotnet-patterns

# .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. ```csharp // 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. ```csharp // Good: Explicit access modifiers and nullability public sealed class UserService { private readonly IUserRepository _repository; private readonly ILogger<UserService> _logger; public UserService(IUserRepository repository, ILogger<UserService> logger) { _repository = repository ?? throw new ArgumentNullException(nameof(repository)); _logger = logger ?? throw new ArgumentNullException(nameof(logger)); } public async Task<User?> FindByIdAsync(Guid i...