Get RowIndex in ASP.Net GridView RowCommand event

In my grid veiw Row command sub section i used e.command argument. But it always return empty string like ""

my code is like this........

 Protected Sub GridView1_RowCommand(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewCommandEventArgs) Handles GridView1.RowCommand

        Dim rowindex As Integer = Convert.ToInt32(e.CommandArgument)

  End Sub

I want row index to do type cast my textbox inside my grid itemtemplate...........

plz suggest solution for this.............