index was out of range. must be non-negative and less than while deleting a row

protected void rad_grid_ItemDeleted(object sender, GridDeletedEventArgs e)
    {        
            if (e.Exception != null)
            {
                e.ExceptionHandled = true;

                DisplayMessage(true, "customer" + e.Item.OwnerTableView.DataKeyValues[e.Item.ItemIndex]["CustomerID"] + "cannot be deleted:reason is" + e.Exception.Message);
            }
            else
            {
                DisplayMessage(false, "customer" + e.Item.OwnerTableView.DataKeyValues[e.Item.ItemIndex]["CustomerID"] + "deleted");
            }
        }