MVC Partial Class For Rule Validation

I have 2 projects. A data project, which contains my database and my Entity Framework model. I have table called 'User', and then have a generated EF class for user. I am trying to add a partial class:

using System;
using System.Collections.Generic;
using System.Data.Linq;
using System.Linq;
using System.Text;
namespace Data
{
public partial class user
{
public bool isValid
{
get {
return (GetRuleViolations().Count()==0);
}
}
public IEnumerable<RuleViolation> GetRuleViolations()
{
yield break;
}
partialvoid OnValidate(ChangeAction action)
{
if (isValid)
throw new ApplicationException("Rule violation prevents saving");
}
}
public class RuleViolation
{
public string ErrorMessage { get; private set; }
public string PropertyName { get; private set; }
public RuleViolation (string errorMessage)
{
ErrorMessage = errorMessage;
}
public RuleViolation(string errorMessage, string propertyName)
{
ErrorMessage = errorMessage;
PropertyName = propertyName;
}
}
}

This is following the MVC 1.0 NerdDinner example. However, I am getting a design time error on the OnValidate method:

partial void OnValidate(ChangeAction action)
{
if (isValid)
throw new ApplicationException("Rule violation prevents saving");
}

No definining declaration found for implimenting declaration of partial method 'void OnValidate(ChangeAction action)' What am I doing wrong?