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.