C#•7mo ago

ASP.NET: Elegant controller <-> service interaction

Hey! I am looking for an elegant controller <-> service interaction. Example (pseudocode):

[ApiController]
[Route("[controller]")]
public class CarController(ICarService carService) : ControllerBase
{
    public async Task<IActionResult> UpdateCar(CarDto carDto)
    {
        var (car, statusCode) = await carService.UpdateCar(carDto);
        
        if (statusCode != HttpStatusCode.OK)
        {
            return StatusCode((int)statusCode);
        }

        return Ok(car);
    }
}

[ApiController]
[Route("[controller]")]
public class CarController(ICarService carService) : ControllerBase
{
    public async Task<IActionResult> UpdateCar(CarDto carDto)
    {
        var (car, statusCode) = await carService.UpdateCar(carDto);
        
        if (statusCode != HttpStatusCode.OK)
        {
            return StatusCode((int)statusCode);
        }

        return Ok(car);
    }
}

My issue with this code: The service layer is returning an HTTP status code although the car service shouldn't have to do anything with HTTP stuff. I thought about adding a dedicated enum which would kinda imitate some of the HTTP status codes (OK, NotFound, Conflict). Other ideas: - Throw custom exceptions (don't like this one, exceptions are ugly) Do you have a more convenient solution for this issue? How do you deal with this kind of stuff? Thanks in advance! Related: - https://stackoverflow.com/questions/76990166/what-should-the-service-layer-return-to-the-controller-when-validating-data-in-s - https://www.reddit.com/r/dotnet/comments/yyix35/mvc_how_do_you_return_failures_from_services/

7 Replies

Keswiik•7mo ago

At work we'd normally use exceptions for this type of flow control, but my day job is java and our services aren't implemented within the API itself (all messaging through a broker such as rabbitmq). I don't see any harm returning an internal enum that you can map to HTTP statuses.

Pobiega•7mo ago

If the errors are meaningfully different, I would probably go with a result type (there is a tag with a bunch of result type libs) Might also want to look at something like Immediate.Handlers

kurumi•7mo ago

I usually return Result<T>, so I can set it success or failer with error message

qqdevOP•7mo ago

Thanks! I will probably return a tuple because it’s not always an "either a or b" scenario. Example: Was the entity created or updated? I could also return a Result<(Entity, CreatedOrUpdatedEnum> in that case I guess

Pobiega•7mo ago

might be a good usecase for OneOf where you could return either a EntityUpdatedResult, EntityCreatedResult or one of a list of errors a bit unergonomic to deal with in C# imho, since there just isnt language support for DUs

qqdevOP•7mo ago

Yeah that’s what’s holding me kinda back Rust, for example, is build around Results/Options and it’s so ergonomic

Pobiega•7mo ago

yeah Result<T> can be fairly ergonomic, with as singular return and if you dont need exhaustive error matching but full blown OneOf is nuts

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ASP.NET: Elegant controller <-> service interaction