Controller → Service → Repository → Database

[ApiController]
[Route("api/[controller]")]
public class UsersController : ControllerBase
{
    private readonly IUserService _userService;

    public UsersController(IUserService userService)
    {
        _userService = userService;
    }

    [HttpGet("{id}")]
    public async Task<ActionResult<UserDto>> GetById(int id)
    {
        var user = await _userService.GetByIdAsync(id);
        return user is null ? NotFound() : Ok(user);
    }

    [HttpPost]
    public async Task<ActionResult<UserDto>> Create(CreateUserDto dto)
    {
        var user = await _userService.CreateAsync(dto);
        return CreatedAtAction(nameof(GetById), new { id = user.Id }, user);
    }
}

public class UserService : IUserService
{
    private readonly IUserRepository _repository;

    public UserService(IUserRepository repository)
    {
        _repository = repository;
    }

    public async Task<UserDto?> GetByIdAsync(int id)
    {
        var user = await _repository.GetByIdAsync(id);
        return user?.ToDto();
    }
}

// Program.cs
builder.Services.AddScoped<IUserService, UserService>();
builder.Services.AddScoped<IUserRepository, UserRepository>();

public class ApiResponse<T>
{
    public bool Success { get; set; }
    public T? Data { get; set; }
    public string? Error { get; set; }
}