public static bool ShorterThan(this UserModel userModel, int threshold)
        {
            var  specification = new ShorterThanSpecification(threshold);
            bool result        = specification.IsSatisfied(userModel);

            return(result);
        }
        public static IQueryable <UserModel> ShorterThan(this IQueryable <UserModel> userModels, int threshold)
        {
            var specification = new ShorterThanSpecification(threshold);

            return(userModels.Where(specification.Expression));
        }