gistfile1.cs

public class Person : IValidatableObject
{
    public string Name { get; set; }
    public string Nickname { get; set; }
    public string Password { get; set; }
    public string PasswordConfirm { get; set; }
    public int Age { get; set; }

    public IEnumerable<ValidationResult> Validate(
        ValidationContext validationContext)
    {
        if (Name.Equals(Nickname))
        {
            yield return new ValidationResult(
                "Name and Nickname cannot be the same",
                new string[] { "Name", "Nickname" });
        }
    }
}