C#•3mo ago

Returning Service result to Controller (Minimal API)

/// <summary>
/// Deletes a reservation by its ID.
/// </summary>
/// <param name="reservationId">ID of the reservation to delete.</param>
public async Task Delete(int reservationId)
{
    try 
    {
        var reservation = await _context.Reservations
        .FirstOrDefaultAsync(r => r.ReservationId == reservationId);

        if (reservation is not null)
        {
            _context.Reservations.Remove(reservation);
            await _context.SaveChangesAsync();
        }
    }
    catch (Exception e)
    {
        Console.WriteLine(e.Message);
    }
}

/// <summary>
/// Deletes a reservation by its ID.
/// </summary>
/// <param name="reservationId">ID of the reservation to delete.</param>
public async Task Delete(int reservationId)
{
    try 
    {
        var reservation = await _context.Reservations
        .FirstOrDefaultAsync(r => r.ReservationId == reservationId);

        if (reservation is not null)
        {
            _context.Reservations.Remove(reservation);
            await _context.SaveChangesAsync();
        }
    }
    catch (Exception e)
    {
        Console.WriteLine(e.Message);
    }
}

I have a method in my service. If my deletion fails, how do I let the controller know it failed? Endpoint for reference:

/// <summary>
/// Deletes a reservation by ID.
/// </summary>
/// <param name="reservationId">ID of the reservation to delete.</param>
/// <returns>
/// 200 OK status code to confirm that the reservation has been deleted.
/// </returns>
[HttpDelete]
[ProducesResponseType(StatusCodes.Status200OK)]
[ProducesResponseType(StatusCodes.Status404NotFound)]
public async Task<IActionResult> DeleteReservation([FromQuery] int reservationId)
{
    var existingReservation = await reservationStorage.Read(reservationId);

    if (existingReservation == null)
    {
        return NotFound();
    }

    await reservationStorage.Delete(reservationId);
    return Ok();
}

/// <summary>
/// Deletes a reservation by ID.
/// </summary>
/// <param name="reservationId">ID of the reservation to delete.</param>
/// <returns>
/// 200 OK status code to confirm that the reservation has been deleted.
/// </returns>
[HttpDelete]
[ProducesResponseType(StatusCodes.Status200OK)]
[ProducesResponseType(StatusCodes.Status404NotFound)]
public async Task<IActionResult> DeleteReservation([FromQuery] int reservationId)
{
    var existingReservation = await reservationStorage.Read(reservationId);

    if (existingReservation == null)
    {
        return NotFound();
    }

    await reservationStorage.Delete(reservationId);
    return Ok();
}

31 Replies

packetphysicistOP•3mo ago

I was thinking to have the return type be Task<bool> but I am just wondering if there is a different way to handle it.

Pobiega•3mo ago

Exceptions would be one way, but its frowned upon by many. Personally, I'd use a proper result type.

Kringe•3mo ago

why is exceptions frowned upon?

Pobiega•3mo ago

ie, your Delete method would return a Task<Result>, where Result has a bool and optionally an error message. Because exceptions should be for exceptional things, not control flow or error messages

Kringe•3mo ago

if a deletion fails is that not an exception

Pobiega•3mo ago

a lot of us here on the discord like result types, so theres a pretty large collection of libraries that you could use: $resultlibs

MODiX•3mo ago

see $resultlib

Pobiega•3mo ago

$resultlib

MODiX•3mo ago

- thinker227/Rascal - Remora.Results - mcintyre321/OneOf - altmann/FluentResults - dotnet/dotNext - vkhorikov/CSharpFunctionalExtensions - amantinband/error-or - jscarle/LightResults - Madared/Result

Pobiega•3mo ago

if it fails, sure. but a non-existing ID isnt really an exceptional failure

packetphysicistOP•3mo ago

Yeah but what if database has exceptions and stuff

Pobiega•3mo ago

then exception is fine if the DB connection fails, thats 100% an exception but is me passing a non-existing ID exceptional? I'm not sure it is

Kringe•3mo ago

Okay ty I see

Pobiega•3mo ago

again, you could solve this with exceptions and try/catch but I among many others prefer result types for sitatuations like this

packetphysicistOP•3mo ago

Could you maybe provide a code snippet? Because what I basically want is that if there is an exception, my controller knows my delete didn't delete because of that exception. and return the proper code.

Pobiega•3mo ago

I can do you one better. I made a youtube video on this topic only a few weeks ago. https://www.youtube.com/watch?v=gHZNQe9zh6s

packetphysicistOP•3mo ago

omg youre a youtuber

Pobiega•3mo ago

I mean, uploading a few videos is a pretty low bar...

packetphysicistOP•3mo ago

Do you think this would properly handle my case?

Pobiega•3mo ago

if you dont wanna sit through the theory, https://github.com/jscarle/LightResults is pretty nice

return Result.Ok();
//or
return Result.Fail("Operation failed!");

//in your controller
var result = await Service.Delete(x);
if (result.IsFailed)
{
  return ... // your http error code stuff here
}

return Ok();

return Result.Ok();
//or
return Result.Fail("Operation failed!");

//in your controller
var result = await Service.Delete(x);
if (result.IsFailed)
{
  return ... // your http error code stuff here
}

return Ok();

packetphysicistOP•3mo ago

kk, I will check it out.

Pobiega•3mo ago

I personally tend to use Remora.Results, but its a bit too strict for some people the authors of most of those libs hang around here, or have done in the past but even without a library its a pretty simple concept, as my video demonstrates yes.

packetphysicistOP•3mo ago

Why Remora? Any reason?

Pobiega•3mo ago

because it forces errors to be objects you absolutely dont have to use remora just necause its my personal preference :p I also tend to use quite a bit of other Remora libraries in my recent projects, and they all use that internally so it just makes sense there

packetphysicistOP•3mo ago

Aren't they already objects..? Exception is an object, no? Or am I completely misunderstanding

Pobiega•3mo ago

No you're fine. Exceptions are objects. But in cases where you don't have an exception, but still want information about the error

packetphysicistOP•3mo ago

If there's no exception there's no error, right? Or are exceptions only handled errors?

Pobiega•3mo ago

exceptions are almost always errors, but there are exceptions to most rules. There are also errors that are not exceptions I mean "error" here as anything that can cause a method to fail that might be "the user is stupid and sent a string instead of an int" or "no hit for given id 5 in database" these may or may not be exceptions, but they are certainly errors

MODiX•3mo ago

Pobiega

was it... this?

[HttpGet]
public async Task<ActionResult<TodoListDto>> Get(int id)
{
    var query = new GetTodoListQuery()
    {
        Id = id
    };

    var result = await _mediator.Send(query);
    if (!result.IsSuccess)
    {
        return result.Error switch
        {
            NotFoundError notFoundError => NotFound(notFoundError.Message),
            ValidationError validationError => BadRequest(validationError.ValidationFailures),
            _ => Problem(detail: result.Error.Message, title: "Internal Server Error", statusCode: 500)
        };
    }

     return _mapper.Map<TodoListDto>(result.Entity);
}

[HttpGet]
public async Task<ActionResult<TodoListDto>> Get(int id)
{
    var query = new GetTodoListQuery()
    {
        Id = id
    };

    var result = await _mediator.Send(query);
    if (!result.IsSuccess)
    {
        return result.Error switch
        {
            NotFoundError notFoundError => NotFound(notFoundError.Message),
            ValidationError validationError => BadRequest(validationError.ValidationFailures),
            _ => Problem(detail: result.Error.Message, title: "Internal Server Error", statusCode: 500)
        };
    }

     return _mapper.Map<TodoListDto>(result.Entity);
}

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Pobiega•3mo ago

here is an example NotFoundError => ok send the user a 404 not found ValidationError => send the user a 400 bad request some other error? => send the user a 500 Internal server error no error? send the user a 200 ok with the mapped result

packetphysicistOP•3mo ago

Mhmmmmmm Okay I think I'm getting the gist of it

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Returning Service result to Controller (Minimal API)