استفاده از استاندارد نتیجه در API با .NET 9.0

public class Result<T>
{
    public bool IsSuccess { get; }
    public T? Value { get; }
    public string? ErrorMessage { get; }

    private Result(T value)
    {
        IsSuccess = true;
        Value = value;
    }

    private Result(string errorMessage)
    {
        IsSuccess = false;
        ErrorMessage = errorMessage;
    }

    public static Result<T> Success(T value) => new(value);
    public static Result<T> Failure(string errorMessage) => new(errorMessage);
}

public class UserService
{
    private readonly Dictionary<int, string> _users = new()
    {
        { 1, "Henrique" },
        { 2, "Marta" }
    };

    public Result<string> GetUserById(int id)
    {
        if (!_users.TryGetValue(id, out var user))
        {
            return Result<string>.Failure("Usuário não encontrado.");
        }
        return Result<string>.Success(user);
    }
}

[ApiController]
[Route("api/users")]
public class UsersController : ControllerBase
{
    private readonly UserService _userService = new();

    [HttpGet("{id}")]
    public IActionResult GetUser(int id)
    {
        var result = _userService.GetUserById(id);

        if (!result.IsSuccess)
        {
            return NotFound(new { error = result.ErrorMessage });
        }

        return Ok(new { user = result.Value });
    }
}

{
    "user": "Henrique"
}

{
    "error": "Usuário não encontrado."
}

public class Error
{
    public string Code { get; }
    public string Message { get; }

    public Error(string code, string message)
    {
        Code = code;
        Message = message;
    }
}

public class Result<T>
{
    public bool IsSuccess { get; }
    public T? Value { get; }
    public Error? Error { get; }

    private Result(T value)
    {
        IsSuccess = true;
        Value = value;
    }

    private Result(Error error)
    {
        IsSuccess = false;
        Error = error;
    }

    public static Result<T> Success(T value) => new(value);
    public static Result<T> Failure(string code, string message) => new(new Error(code, message));
}

public Result<string> GetUserById(int id)
{
    if (!_users.TryGetValue(id, out var user))
    {
        return Result<string>.Failure("USER_NOT_FOUND", "Usuário não encontrado.");
    }
    return Result<string>.Success(user);
}

[HttpGet("{id}")]
public IActionResult GetUser(int id)
{
    var result = _userService.GetUserById(id);

    if (!result.IsSuccess)
    {
        return NotFound(new { errorCode = result.Error!.Code, message = result.Error.Message });
    }

    return Ok(new { user = result.Value });
}

{
    "errorCode": "USER_NOT_FOUND",
    "message": "Usuário não encontrado."
}