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

I was also struggling with this in a .NET Core 3.1 API, where I wanted the result to include $type attribute.

As suggested, install the correct package and then 'AddNewtonsoftJson'.

I wanted the $type field to be added to show the derived type handling, to get that

services.AddControllers().AddNewtonsoftJson(options => 
{ 
    options.SerializerSettings.TypeNameHandling = Newtonsoft.Json.TypeNameHandling.All;
});