How To Check Old-value VS New-value For A Linq-To-SQL OnValidate Extensibility Method

All --

Please  help.

I need to know how to check old-value VS new-value for a Linq-To-SQL OnValidate Extensibility Method.

Below is some sample code that shows, more-or-less, what I am trying to do.

public partial class MyObject
{
 #region Extensions


 partial void OnValidate(System.Data.Linq.ChangeAction action)
 {
  if (action == System.Data.Linq.ChangeAction.Update)
  {
   if ((Ssn_Value_Old) == (Ssn_Value_New))
   {
    //Continue. The new-value is the same as the old-value; so, do not bother checking for existence.
   }
   else
   {
    if (this.IsExistingSsn(Ssn_Value_New))
    {
     throw new System.ApplicationException("The input is not valid. The new-value for the SSN is already existing.");
    }
    else
    {
     //Continue. The new-ssn does not already exist.
    }
   }
  }
  else
  {
   //Continue. This is not an update operation.
  }
 }


 #endregion //Extensions
}



Do you know how to do this without a separate lookup?

Please advise.

Thank you.

-- Mark Kamoski