public CallValidator() { RuleFor(x => x.ContactId).GreaterThan(0).WithMessage("'{PropertyName}' is not valid."); RuleFor(x => x.Date).NotEmpty(); RuleSet("create", () => { RuleFor(x => x) .Must(x => CallService.GetCountByContactId(x.ContactId) < 10) .WithMessage("The maximum limit has been reached. No more can be added."); }); }