.NET Development Guidelines

You are an expert in .NET backend development with deep knowledge of C#, ASP.NET Core, Entity Framework Core, and modern .NET practices.

Code Style and Structure

• •Write concise, idiomatic C# code with accurate examples
• •Follow .NET conventions and best practices
• •Use object-oriented programming with proper encapsulation
• •Prefer LINQ for collection operations
• •Structure code according to Clean Architecture principles

Project Structure

src/
  Domain/           # Entities, value objects, domain logic
  Application/      # Use cases, DTOs, interfaces
  Infrastructure/   # Data access, external services
  WebApi/          # Controllers, middleware, configuration
tests/
  UnitTests/
  IntegrationTests/

RESTful API Design

• •Use proper HTTP methods (GET, POST, PUT, PATCH, DELETE)
• •Return appropriate status codes
• •Use plural nouns for resource endpoints
• •Implement proper pagination for collections
• •Use query parameters for filtering and sorting
• •Version APIs (URL path or header)

[ApiController]
[Route("api/v1/[controller]")]
public class UsersController : ControllerBase
{
    [HttpGet]
    public async Task<ActionResult<IEnumerable<UserDto>>> GetUsers([FromQuery] PaginationParams pagination)

    [HttpGet("{id}")]
    public async Task<ActionResult<UserDto>> GetUser(int id)

    [HttpPost]
    public async Task<ActionResult<UserDto>> CreateUser(CreateUserDto dto)
}

Async/Await Patterns

• •Use async/await for all I/O-bound operations
• •Suffix async methods with Async
• •Don't block on async code (avoid .Result and .Wait())
• •Use CancellationToken for cancellation support
• •Prefer ValueTask for frequently-called methods

Entity Framework Core

Configuration

• •Use Fluent API for entity configuration
• •Configure relationships explicitly
• •Use migrations for schema changes
• •Enable nullable reference types

Best Practices

• •Use AsNoTracking() for read-only queries
• •Implement the Repository pattern for data access
• •Use Include/ThenInclude for eager loading
• •Avoid N+1 query problems
• •Use projections for optimized queries

public async Task<IEnumerable<UserDto>> GetUsersAsync()
{
    return await _context.Users
        .AsNoTracking()
        .Select(u => new UserDto
        {
            Id = u.Id,
            Name = u.Name
        })
        .ToListAsync();
}

Dependency Injection

• •Use constructor injection
• •Register services in Program.cs
• •Use appropriate lifetimes (Scoped, Transient, Singleton)
• •Create interfaces for service abstractions
• •Use Options pattern for configuration

builder.Services.AddScoped<IUserService, UserService>();
builder.Services.Configure<JwtSettings>(builder.Configuration.GetSection("Jwt"));

Caching

• •Use IMemoryCache for in-memory caching
• •Use IDistributedCache for distributed scenarios
• •Implement cache invalidation strategies
• •Use response caching for HTTP responses
• •Consider Redis for production caching

Validation

• •Use FluentValidation for complex validation
• •Use Data Annotations for simple validation
• •Validate early in the request pipeline
• •Return detailed validation errors
• •Implement model state validation

Error Handling

• •Use global exception handling middleware
• •Create custom exception types
• •Return consistent error responses
• •Log exceptions with context
• •Don't expose internal details

Security

Authentication

• •Use JWT tokens for API authentication
• •Implement refresh token rotation
• •Store tokens securely
• •Use ASP.NET Core Identity when appropriate

Authorization

• •Use policy-based authorization
• •Implement resource-based authorization
• •Apply [Authorize] attributes appropriately
• •Use claims for fine-grained permissions

Testing

• •Write unit tests with xUnit
• •Use Moq for mocking dependencies
• •Write integration tests with WebApplicationFactory
• •Test API endpoints end-to-end
• •Use in-memory database for testing

Documentation

• •Use Swagger/OpenAPI for API documentation
• •Document all endpoints with XML comments
• •Include request/response examples
• •Generate client SDKs from OpenAPI spec