using System;

using System.ComponentModel.DataAnnotations;

using System.Collections.Generic;

using System.Linq;

using System.ComponentModel;

​

public class Program

{

    public static void Main()

    {

        /* Should not pass validation */

        var obj = new MyClass()

        {Value = "123456"};

        /* Should not pass validation */

        var obj2 = new MyClass()

        {Value = "123456"};

        /* Add custom provider to just the first object */

        var provider = new AssociatedMetadataTypeTypeDescriptionProvider(typeof (MyClass), typeof (MyClassMeta));

        TypeDescriptor.AddProvider(provider, obj);

        Console.WriteLine("obj:");

        Validate(obj);

        Console.WriteLine("obj2:");

        Validate(obj2);

    }

​

    private static void Validate(object obj)

    {

        ValidationContext context = new ValidationContext(obj, null, null);

        List<ValidationResult> results = new List<ValidationResult>();

        bool valid = Validator.TryValidateObject(obj, context, results, true);

        if (!valid)

        {

            foreach (ValidationResult vr in results)

            {

                Console.Write("Member Name:{0}", vr.MemberNames.First());

                Console.WriteLine(" - {0}", vr.ErrorMessage);

            }

        }

        else

        {

            Console.WriteLine("I am valid.");

        }

    }

}

​

public class MyClass

{

    [Required]

    public string Value

    {

        get;

        set;

    }

}

​

public class MyClassMeta

{

    [MaxLength(5)]

    public string Value

    {

        get;

        set;

    }

}