Evitar mapeo redundante en Newtonsoft

El Global.asax debería quedar similar a la siguiente forma:

using Newtonsoft.Json;
using System.Web.Http;

namespace _2._0.Service
{
    public class WebApiApplication : System.Web.HttpApplication
    {
        protected void Application_Start()
        {
            GlobalConfiguration.Configure(WebApiConfig.Register);

            JsonConvert.DefaultSettings = (() => new JsonSerializerSettings { ReferenceLoopHandling = ReferenceLoopHandling.Ignore });
        }
    }
}