listbox data through excel sheet

String conStr1 = "Provider=Microsoft.Jet.OLEDB.4.0;" + "Data Source=" + Server.MapPath("/portal/files/allcity.xls") + ";" + "Extended Properties=Excel 8.0;";

                OleDbConnection con1 = new OleDbConnection(conStr1);

                con1.Open();

                string k1 = "select state from  [Sheet1$] group by state";

                cm = new OleDbCommand(k1, con1);

                dr = cm.ExecuteReader();

                ListBox3.DataSource = dr;

                ListBox3.DataTextField = "state";

                ListBox3.DataBind();

                ListBox3.Items.Insert(0, "Select");              

                dr.Close();