AutoCAD Inventor :: Cancel Deletion With On Delete

I want to cancel deletion of certain Part Feature (where PartFeature.Name  starts with ''I_''). In my dll, I capture « DocumentEvents.OnDelete ».

private void PartDocument_OnDelete(object o, BeforeAfterEnum beforeAfter, NameValueMap context, out HandlingCodeEnum handlingCode)
{
if (beforeAfter == BeforeAfterEnum.Before)
{
if (((PartFeature)o).Name.StartsWith(‘’I_’’))
{
MessageBox.Show(‘’You cannot delete ’’I_*’’ part features.’’);
// MISSING CODE HERE TO CANCEL DELETION !!!
}
}
}

First I thought that putting « handlingCode » to « HandlingCodeEnum.evtCancelHandle » would do the job, but when I read the API, it says that Inventor doesn’t care about that output argument. Then, how can I cancel the deletion of an object when capturing ‘On Delete’ event ?