using System.ComponentModel.DataAnnotations;

using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("asas");

        var prueba = new Model();

        var vc = new ValidationContext(prueba, null, null);

        var isValid = Validator.TryValidateObject(prueba, vc, null);

        Console.WriteLine("isValid:" + isValid.ToString());

        Console.WriteLine(prueba.cvv);

    }

    public class Model

    {

        [Required, StringLength(3)]

        public string cvv { get; set; }

    }

}