OnlyRootContractResolver.cs

    public class OnlyRootContractResolver : CamelCasePropertyNamesContractResolver
    {
        protected Type _root;
        protected List<string> _included;

        public OnlyRootContractResolver(Type root, IEnumerable<string> included)
        {
            _root = root;
            _included = new List<string>(included ?? new string[0]);
        }

        protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
        {
            var res = base.CreateProperties(type, memberSerialization);
            if (type == _root)
                return res;

            var qry = from t in res
                      where _included.Contains(t.PropertyName) || Type.GetTypeCode(t.PropertyType) != TypeCode.Object
                      select t;
            return qry.ToList();
        }
    }