NewtonSoft JSON not raising Exception when using MissingMemberHandling.Error

Question

We use the Newtonsoft Json converter to deserialise API requests. As we don't want to receive data/members which are not part of the request class in the BackEnd, we set SerializerSettings.MissingMemberHandling to MissingMemberHandling.Error:

services.AddControllers().AddNewtonsoftJson(a =>
    {
        a.SerializerSettings.MissingMemberHandling = MissingMemberHandling.Error;
    }

But instead of receiving an Exception, we end up with a 'null' request object for the API-call:

Why don't we get an Exception?

Answer 1

I found the problem: my controller was configurered like this:

[Route("api/[controller]")]
public class MyController
{
}

Since everything was working as expected before we added the missing member setting, I did not think of the missing attribute [ApiController]. Adding this, made this controller act like the others regarding the Json serialisation!

[Route("api/[controller]")]
[ApiController]  // <- added this
public class MyController
{
}

To be sure this isn’t forgotten, we wrote a test which checks all controller classes for this attribute.

Answer 2

I don't know how you configured Newtonsoft.Json. I make a working example. Here is the steps.

1. Add the following Nuget package.

   Microsoft.AspNetCore.Mvc.NewtonsoftJson

2. Configure it in Startup.cs.

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllersWithViews()
            .AddNewtonsoftJson(option=>
            {
                option.SerializerSettings.MissingMemberHandling = MissingMemberHandling.Error;
            });
    }
   

3. Add a request action and the model. This is the all controller code.

   [ApiController]
   [Route("[controller]")]
   public class ValController:Controller
   {
    [AllowAnonymous]
    [HttpPost]
    public IActionResult LoginAsync([FromBody]Login login)
    {
        return Ok(login);
    }
   }
   public class Login
   {
    public string comm { get; set; }
   }
   

4. Then I access the action.