protected override Expression <Func <FieldListAssociation, bool> > FindExisting(FieldListAssociation record)
 => existing
 => existing.FieldId == record.FieldId &&
 existing.FieldListId == record.FieldListId;
        protected override IEnumerable <object> EnumerateReferences(FieldListAssociation record)
        {
            yield return(record.Field);

            yield return(record.FieldList);
        }