JsonResult(object) causes “The collection type 'Newtonsoft.Json.Linq.JToken' is not supported.”

Question

I upgraded an existing ASP.NET Core 2.2 project to 3.0. I have a method that returns JSON which worked in 2.2, but in 3.0, it causes \"The collection type \'Newtonsoft.Json.Linq

Answer 1

@sabiland answer helped me, small changes

1. added in .csproj reference to NewtonsoftJson, as below

< PackageReference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" Version="3.0.0" />

2. adde in Startup.cs, in method ConfigureServices, AddMvcCore

   services.AddMvcCore()
           .AddNewtonsoftJson();