detailsview rowindex

hi all
iam using detailsview to edit the data
below code is to get the textbox values into list, but iam geting error as 
Error 20 'System.Web.UI.WebControls.DetailsViewUpdateEventArgs' does not contain a definition for 'RowIndex' and no extension method 'RowIndex' accepting a first argument of type 'System.Web.UI.WebControls.DetailsViewUpdateEventArgs' could be found (are you missing a using directive or an assembly reference?) 
List<TextBox> tbxlist = new List<TextBox>(); foreach (Control item in DetailsView1.Rows[e.RowIndex].Controls) { foreach (Control childItem in item.Controls) { if (childItem is TextBox) { TextBox tbx = childItem as TextBox; tbxlist.Add(tbx); } }
}