Controlling SerializerSettings for ASP.Net Core 2.0 returning IActionResult

Question

I've created an ASP.NET 2.0 webapi and am trying to return an abstract type from a method which returns IActionResult, i.e.

    // GET api/trades/5
    [HttpGet("{id}", Name = "GetTrade")]
    [ProducesResponseType(typeof(Trade), 200)] 
    [ProducesResponseType(404)]
    public IActionResult Get(int id)
    {
        var item = _context.Trades.FirstOrDefault(trade => trade.Id == id);
        if (item == null)
        {
            return NotFound();
        }
        return Ok(item);
    }

The Trade type is an abstract base class, I want the serialised JSON to include the $type attribute so the client can deserialise to the correct concrete type. The code below controls the output serialiser if I change the method to return Trade (the json returned contains a $type attribute with the concrete type name) but not IActionResult (no $type attribute).

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        services
            .AddDbContext<RiskSystemDbContext>(opt => opt.UseInMemoryDatabase("RiskSystemDb"));

        services
            .AddMvc(options => {})
            .AddJsonOptions(options =>
            {
                options.SerializerSettings.Converters.Add(new StringEnumConverter());
                options.SerializerSettings.NullValueHandling = NullValueHandling.Ignore;
                options.SerializerSettings.TypeNameHandling = TypeNameHandling.Auto;
            });
    }

How do I set TypeNameHandling for an IActionResult?

Edit:

For a class FutureTrade : Trade {} I expect

{
  "$type": "RiskSystem.Model.FutureTrade, RiskSystem.Model",
  "id": 1,
  "createdDateTime": "2018-04-12T15:59:11.3680885+12:00"
  ...
}

Getting

{
  "id": 1,
  "createdDateTime": "2018-04-12T15:59:11.3680885+12:00"
  ...
}

The following works as expected

    // GET api/trades
    [HttpGet]
    public IEnumerable<Trade> Get()
    {
        return _context.Trades.ToList();
    }

Regards Dave

Please include some expected and actual json object structure that is returned to your JS client. This will help everyone to visualize your issue. — Thangadurai
– Thangadurai, Commented Apr 12, 2018 at 5:44
Can you try with this option options.SerializerSettings.TypeNameHandling = TypeNameHandling.Objects — Thangadurai
– Thangadurai, Commented Apr 12, 2018 at 7:46
Thanks, that seems to work consistently. Add as a proper solution and I'll mark it as the answer. — David Waterworth
– David Waterworth, Commented Apr 12, 2018 at 16:07
@user2981639 by default web api uses JSON.NET serializer settings as TypeNameHandling.None so the $type is not included, you can change it as per your requirement. — Niladri
– Niladri, Commented Apr 13, 2018 at 12:38

Thangadurai · Accepted Answer · 2018-04-14 05:40:41Z

1

Changing the TypeNameHandling from Auto to Objects will force the JSON serializer to emit the type name always.

Please change your TypeNameHandling from

options.SerializerSettings.TypeNameHandling = TypeNameHandling.Auto;

to

options.SerializerSettings.TypeNameHandling = TypeNameHandling.Objects

answered Apr 14, 2018 at 5:40

Thangadurai

2,62129 silver badges32 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Controlling SerializerSettings for ASP.Net Core 2.0 returning IActionResult

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related