public class RegisterUserUseCase
{
    public IActionResult Execute(HttpRequest request)  // Coupled to ASP.NET
    {
        var email = request.Form["email"];
        var password = request.Form["password"];

        if (string.IsNullOrEmpty(email))
            return new BadRequestResult();  // HTTP-specific response

        var user = new User(email, password);
        _repository.Save(user);

        return new OkObjectResult(new { id = user.Id });  // JSON response
    }
}

// application/ports/input/RegisterUserCommand.cs
public record RegisterUserCommand(
    string Email,
    string Password,
    string Name
);

// application/ports/output/RegisterUserResult.cs
public record RegisterUserResult(
    string UserId,
    string Email,
    DateTime CreatedAt
);

// application/usecases/RegisterUserUseCase.cs
public class RegisterUserUseCase
{
    private readonly IUserRepository _repository;
    private readonly IPasswordHasher _hasher;

    public RegisterUserResult Execute(RegisterUserCommand command)
    {
        if (string.IsNullOrEmpty(command.Email))
            throw new ValidationException("Email required");

        var hashedPassword = _hasher.Hash(command.Password);
        var user = new User(command.Email, hashedPassword, command.Name);
        _repository.Save(user);

        return new RegisterUserResult(
            user.Id.Value,
            user.Email.Value,
            user.CreatedAt
        );
    }
}

// interface_adapters/controllers/UserController.cs
[ApiController]
public class UserController : ControllerBase
{
    [HttpPost]
    public IActionResult Register([FromBody] RegisterRequest request)
    {
        var command = new RegisterUserCommand(
            request.Email,
            request.Password,
            request.Name
        );

        var result = _useCase.Execute(command);

        return Ok(new { userId = result.UserId });
    }
}