ASP.Net Core Error JSON

Question

I'm playing a bit with ASP.NET Core. I'm creating a basic webapi. I'd like to show a JSON error when there is a problem.

The printscreen shows want I want on my screen. The only problem is that it's send with a statuscode of 200.

catch (NullReferenceException e)
{
    return Json(NotFound(e.Message));
}

I could solve it by doing this:

return NotFound(new JsonResult(e.Message) {StatusCode = 404);

But I don't like this because now you can specify statuscode 500 with a NotFound.

Can someone put me in the correct direction?

Sincerely, Brecht

The second piece of code is the correct way to do it. You "could" specify a 500 as the status code but why would you, you are in control of the api. — Stephen Brickner
– Stephen Brickner, Commented Sep 6, 2016 at 15:54
You don't have to set StatusCode on the JsonResult. The NotFound method is already doing that. — Matias Cicero
– Matias Cicero, Commented Sep 6, 2016 at 15:55

Swagata Prateek · Accepted Answer · 2016-09-06 16:18:35Z

5

Can't you do something like return NotFound(e.Message);

Or you might have your own error document format and go for return NotFound(new ErrorDocument(e.message));

If you have to return with a JsonResult then go for something like the following:

return new JsonResult(YourObject) { StatusCode = (int)HttpStatusCode.NotFound };

Now you have full control over response format and your status code too. You can even attach serializer settings if need be. :)

answered Sep 6, 2016 at 16:18

Swagata Prateek

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3 Comments

ErazerBrecht Over a year ago

If I do return NotFound(e.Message); then the error message is displayed as plain text because e.Message is a normal 'string'. My other errors that check the ModelState are in JSON. And it like to have consistency. I created now and class for making errors. I'll post my new solution seperated. Thanks for showing me the way. I was to busy using NotFound(). It totally forgot about just using 'new JsonResult' as return

Swagata Prateek Over a year ago

I understand the modelstate checks. If you want a better hand on this, I'd suggest you to use an Exception Filter described a bit about here. Then all you ever have to worry about is throwing a proper exception and your controllers would look nice without the global try-catch block surrounding the main code. Just a thought. And yes, error consistency is a good thing. :)

ErazerBrecht Over a year ago

Thank you for posting that link. I will check that out! Have a nice day!

Community · Accepted Answer · 2017-05-23 11:46:07Z

3

EDIT: Found a much better solution here on stackoverflow.

Thank you Swagata Prateek for reminding me to just use a return new JsonResult(). I did solve me problem on this way.

public class Error
{
    public string Message { get; }
    public int StatusCode { get; }

    public Error(string message, HttpStatusCode statusCode)
    {
        Message = message;
        StatusCode = (int)statusCode;
    }
}    


[HttpGet("{id}")]
public IActionResult Get(int id)
{
    try
    {
       return Ok(_manager.GetPokemon(id));
    }
    catch (NullReferenceException e)
    {
       var error = new Error(e.Message, HttpStatusCode.NotFound);
       return new JsonResult(error) {StatusCode = error.StatusCode};
    }
}

edited May 23, 2017 at 11:46

CommunityBot

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answered Sep 6, 2016 at 17:42

ErazerBrecht

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