services.AddControllers().AddNewtonsoftJson() doesn't override System.Text.Json

From @Yannick183 on Wednesday, August 28, 2019 8:16:27 AM

Issue Title

services.AddControllers().AddNewtonsoftJson() doesn’t seem to override System.Text.Json

General

I tried to upgrade a WebAPI project from dotnetcore 2.2 to version 3 but I’m facing some issues with Json serialization.

Using version 3.0.100-preview8-013656, I tried to override System.Text.Json by adding this to ConfigureServices

services.AddControllers().AddNewtonsoftJson(options =>
{
    options.SerializerSettings.Converters.Add(new StringEnumConverter(new CamelCaseNamingStrategy()));
    options.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
});

Some of my controller endpoints fail with a HTTP500 error because of some circular references that should have been prevented by the [JsonIgnore] attribute. The error is the following : System.Text.Json.JsonException: CurrentDepth (32) is equal to or larger than the maximum allowed depth of 32.

As you can see, the error comes from System.Text.Json.JsonException which I suspect means that Newtonsoft.Json isn’t used by the controller to serialize the response.

I use ModelMetadataType to add [JsonIgnore] to some attributes like this. I even tried adding System.Text.Json.Serialization.JsonIgnore to the property but without any result.

    [ModelMetadataType(typeof(ISomeEntityClassMetadata))]
    public partial class SomeEntityClass : ISomeEntityClassMetadata
    {
    }

    public interface ISomeEntityClassMetadata
    {
        [System.Text.Json.Serialization.JsonIgnore]
        [JsonIgnore]
        SomeOtherEntityClass SomeOtherEntityNavigation { get; set; }
    }

Copied from original issue: dotnet/core#3269

[anaximander23]

Just ran into this myself; I have to say, it’s very strange that the .AddNewtonsoftJson() method behaves in this way - that is, that it’s available, and doesn’t throw an error, when the relevant NuGet package isn’t even installed.

• If it’s doing something useful (ie. something other than replacing the deserialiser in use during model binding) then maybe the method name should be made more explicit to clarify what it actually does?
• If it’s not doing something useful (ie. it’s intended solely to change the deserialiser in use during model binding, and without the NuGet package it just silently does nothing) then perhaps it should be declared inside of that NuGet package so that it’s not accessible when it’s not going to have the desired effect?

Either way, while you’re right, it would be nice if the documentation properly explained how this should work, it would be even nicer if the code didn’t let developers get into this baffling situation.

[Yannick183]

OK now I feel stupid. @remyjette I realized I didn’t have Microsoft.AspNetCore.Mvc.NewtonsoftJson I only had Newtonsoft.Json installed but since I had the .AddNewtonsoftJson() extension method available I thought it was enough. I was unable to find it in NuGet GUI Microsoft.AspNetCore.Mvc.NewtonsoftJson so my guess was that package was used for previous versions only. I then tried to install it from command line Install-Package Microsoft.AspNetCore.Mvc.NewtonsoftJson -Version 3.0.0-preview8.19405.7 and it worked. Now System.Text.Json is overriden as expected and the circular reference problem is gone.

I don’t know why I couldn’t find the package from NuGet GUI though. You can see below that the search term doesn’t provide any result for Microsoft.AspNetCore.Mvc.NewtonsoftJson but the command line worked.

Using Visual Studio 2019 16.3.0 Preview 2.0