oracle connection using dll

OleDbConnection con = new OleDbConnection("connection string");
           OleDbCommand cmd = con.CreateCommand();
           cmd.CommandText = "select sb_no from shipbill where sb_no='4790421'";
           con.Open();
           OleDbDataReader dr = cmd.ExecuteReader();
           while (dr.Read())
           {
               textBox2.Text = dr["sb_no"].ToString();
           }