C#MYSQL maxの値をクエリした結果

MySqlConnection conn = new MySqlConnection(connetStr);
            //       
            String data = DateTime.Now.ToString("yyyy-MM-dd");
            //    
            Double MaxNumber = 0.0;
            Double TotalNumber = 0.0;
            //           - DayMax
            conn.Open();
            //        
            String data_ym = DateTime.Now.ToString("yyyyMM");
            string tablename = data_ym+ "wzys";
            String sql_work = "SELECT max(wzEventEnergy) FROM " + tablename + " WHERE DATE_FORMAT(acquisitionTime,'%Y-%m-%d')='" + data + "'";
            cmd = new MySqlCommand(sql_work, conn);
            readers = cmd.ExecuteReader();
            while (readers.Read())
            {
                Double number= readers.GetDouble(0);
            }
            conn.Close();

組合せクエリーの結果に対するクエリー

Double number= readers.GetDouble(0);