How to alert to GridView

I use a GridView to connection to a TableAdapter by a ObjectDataSource

and I add a partial calss to the TableAdapter, and add a new update method
like:

-----------------------------------------------------------------------
public virtual int Update2(int Pred, ..)
{
if (Some Conndition)
return 0;
else
return Update(...)

}
----------------------------------------------------------------------------

In some condition, it will update no row. How can I alert to the gridview
that no row updated?
I have try
protected void gvSt_RowUpdated(object sender, GridViewUpdatedEventArgs
e)
{
if (e.AffectedRows < 1)
Label1.Text="®æ¦¡¿ù»~!!";
}
But the e.AffectedRows always return -1 whether the row updated or not