Question

Why does this always return true??

 class Program
    {
        static void Main(string[] args)
        {
            Person p = new Person();
            p.Age = 24;

            ICollection<ValidationResult> results = new Collection<ValidationResult>();
            bool isValid = Validator.TryValidateObject(p, new ValidationContext(p, null, null), results);

            Console.WriteLine("Valid = {0}",isValid);

            foreach (var result in results)
            {
                Console.WriteLine(result.ErrorMessage);
            }

            Console.ReadKey();
        }
    }

    public class Person
    {
        [Required(ErrorMessage = "You have to identify yourself!!")]
        public int Id { get; set; }

        public decimal Age { get; set; }    

    }

what is wrong with my usage??

Answer 1

int is a value type and can never be null.

A new Person() will have an Id of 0, which will satisfy [Required].
In general, [Required] is useless on value types.

To fix this, you can use a nullable int?.