Derived type's properties missing in JSON response from ASP.NET Core API

Question

The JSON response from my ASP.NET Core 3.1 API controller is missing properties. This happens when a property uses a derived type; any properties defined in the derived type but

Answer 1

While the other answers are good and solves the problem, if all you want is the general behavior to be like pre netcore3, you can use the Microsoft.AspNetCore.Mvc.NewtonsoftJson NuGet package and in Startup.cs do:

services.AddControllers().AddNewtonsoftJson()

More info here. This way, you don't need to create any extra json-converters.