Fresh ASP.NET Core API returns empty JSON objects

Question

I have made a .NET Core Web API project to test it out.

My problem is, that the API returns an empty JSON object, when I request the endpoint, which is located at "/api/cars/123" for instance. This happens no matter what kind of object I put in, unless it's any primitive datatype, or an array thereof. The response is always:

{}

The configuration of the application is completely default, on a fresh Visual Studio 2017 installation.

I have the following classes:

Car.cs

namespace Ex6.Entities
{
    public class Car
    {
        private int Id { get; set; }
        private string Make { get; set; }
        private string Model { get; set; }

        public Car(int Id, string Make, string Model)
        {
            this.Id = Id;
            this.Make = Make;
            this.Model = Model;
        }
    }
}

CarsController.cs:

using Microsoft.AspNetCore.Mvc;
using Ex6.Entities;

namespace Ex6.Controllers
{
    [Route("api/[controller]")]
    public class CarsController : Controller
    {

        [HttpGet("{id}")]
        public JsonResult GetCar(int id)
        {
            return Json(new Car(1, "Toyota", "Aygo" ));
        }

    }
}

Am I missing something?

Yeah, updating the question again. It made no difference though :S — Emil Rosenius
– Emil Rosenius, Commented Jun 1, 2017 at 23:17
Yes, and if I try mapping the Car object to a variable before returning it, I can see in the debugger that it's constructed properly. :) — Emil Rosenius
– Emil Rosenius, Commented Jun 1, 2017 at 23:20
I access it through the API, by sending a GET request to "/api/cars/123" for example. — Emil Rosenius
– Emil Rosenius, Commented Jun 1, 2017 at 23:28
Do i need a JSON serializer, or will ASP.NET core take care of it automatically? — Emil Rosenius
– Emil Rosenius, Commented Jun 1, 2017 at 23:29

Camilo Terevinto · Accepted Answer · 2017-06-02 00:02:07Z

59

In order for the JsonSerializer to be able to see and serialize your properties, they need to be public:

public int Id { get; private set; } //the setters can be private
public string Make { get; set; }
public string Model { get; set; }

edited Jun 2, 2017 at 0:02

answered Jun 1, 2017 at 23:07

Camilo Terevinto

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5 Comments

LazyDog Over a year ago

I encountered the same problem when converting a legacy WCF to WebAPI. However, the problem I had was a result class that had all fields and no properties. I added a getter and setter to all the fields to convert them to auto-properties everything worked.

Alen Šimunic Over a year ago

Couldn't find this in documentation. Wish it was easier to find this answer...

Thorbjørn Ravn Andersen Over a year ago

Can JsonSerializer be configured to report these kind of issues?

pwilcox Over a year ago

Not the issue with the OP, but it's worth noting that they also can't be fields, even if public.

freshop Over a year ago

Incredible. Coming from Newtonsoft where fields worked, this had me stumped until I found this answer.

PavelPerov · Accepted Answer · 2022-04-28 10:33:31Z

4

For some reason, Text.JSON doesn't serialize public fields as well, so they need to be properties. This solved the similar issue for me

answered Apr 28, 2022 at 10:33

PavelPerov

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Comments

karayakar · Accepted Answer · 2022-01-11 14:20:43Z

0

Try this by adding configure

services.AddControllersWithViews().AddNewtonsoftJson();

....AddNewtonsoftJson() this should solve the issue.

edited Jan 11, 2022 at 14:20

answered Jan 11, 2022 at 14:11

karayakar

293 bronze badges

1 Comment

SimonGoldstone Over a year ago

Not sure why this was downvoted. This fixed it immediately.

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