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

Migrate from ASP.NET Core 2.2 to 3.0

• Add a package reference to Microsoft.AspNetCore.Mvc.NewtonsoftJson

• Update Startup.ConfigureServices to call AddNewtonsoftJson: services.AddMvc().AddNewtonsoftJson();