DataAnnotations does not work with buddy class. The following code always validate true. Why ?

var isValid = Validator.TryValidateObject(new Customer(), Context, results, true);

and here is the buddy class.

public partial class Customer 
{ 
    public string Name { get; set; } 
    public int Age { get; set; } 
}

[MetadataType(typeof(CustomerMetaData))]
public partial class Customer 
{ 
    public class CustomerMetaData 
    { 
        [Required(ErrorMessage = "You must supply a name for a customer.")]        
        public string Name { get; set; } 
    } 
}

Here is another thread with same question., but no answer. link text