public static void AddValidation(AbstractValidator <Command> v) { v.RuleFor(x => x.Name) .NotEmpty().WithMessage("Please enter name."); v.RuleFor(x => x.Gender) .Equal(0).WithMessage("Invalid gender."); v.RuleForEach(x => x.Locales).ChildRules(locales => { locales.RuleFor(x => x.Name) .NotEmpty().WithMessage("Please enter name."); }); }