WebApiJson.cs

class Program
{
    static void Main(string[] args)
    {
        var server = WebApp.Start("http://+:56789", builder =>
        {
            var configuration = new HttpConfiguration();
            configuration.IncludeErrorDetailPolicy = IncludeErrorDetailPolicy.Always;
            configuration.Routes.MapHttpRoute("default", "api/{controller}");
            configuration.Formatters.JsonFormatter.SerializerSettings.TypeNameHandling = TypeNameHandling.Auto;
            configuration.Formatters.JsonFormatter.SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/html"));
            builder.UseWebApi(configuration);
        });

        var httpClient = new HttpClient();

        var payload = httpClient.GetStringAsync("http://localhost:56789/api/test").Result;

        var sampleResponse = JsonConvert.DeserializeObject<SampleResponse>(payload, new JsonSerializerSettings { TypeNameHandling = TypeNameHandling.Auto });

        server.Dispose();
        Console.WriteLine("done.");
    }
}

public class TestController : ApiController
{
    public SampleResponse Get()
    {
        return new SampleResponse { Name = "Banana", Vehicle = new Car { Brand = "Rimac" }};
    }   
}