Validate a List with Data Annotations

Good I have a list of objects, each object has a checkbox, if the checkbox is true I want to validate that the Name field and the Last name field have a value.

My model:

[ListHasElements(ErrorMessage : "Debe escribir en los casilleros")]
public List<MyObjeto> ListaMyObjeto { get; set; }

This list contains the following fields:

public class MyObjeto{
public bool IsCheck { get; set; }
public string Nombre { get; set; }
public string Apellido { get; set; }
}

This is my custom class

public class ListHasElements : ValidationAttribute
{

    public override bool IsValid(List<PlanillaResult> list)
    {
        if (list != null)
        {
            foreach (var item in list)
            {
                if (item.IsCheck == true)
                {
                    if (string.IsNullOrWhiteSpace(item.Nombre) || string.IsNullOrWhiteSpace(item.Apellido))
                    {

                        return false;
                    }
                }
            }
        }


        return list.Any();
    }
}

But I get the following error: "no suitable member was found to invalidate".

Maybe I'm missing something simple or I'm doing it wrong, what I need is to validate a list through Data Annotations