ExecuteReader требует, чтобы команда имела транзакцию

//ищем в базе даных
                string query = "SELECT * FROM Quotations WHERE ";
                query += "ticker='"+ticker+"' and period='"+ interval + "' and stock_id="+stock_id.ToString()+" and _index="+index.ToString();
                DbCommand command = _wrapper.create_command(_wrapper.create_query(query));
 
                DbDataReader reader = command.ExecuteReader();
                BarPrice bar = null;
                while (reader.Read())
                {                   
                     bar=get_bar_from_reader(reader);
                }
                reader.Close();

        public void read_bars_count()
        {
            _bars_count = 0;
 
            /*string query = "SELECT COUNT(_datetime) FROM Quotations WHERE ";
            query += "ticker=@ticker and period=@period and stock_id=@stock_id ";
            query += "GROUP BY ticker, period, stock_id";*/
            /*string query = "SELECT COUNT(_datetime) FROM Quotations WHERE ";
            query += "ticker='"+ticker+"' and period='"+ interval + "' and stock_id="+stock_id.ToString()+" ";
            query += "GROUP BY ticker, period, stock_id";*/
 
            string query = "SELECT count, beg_loaded, end_loaded, beg_date FROM SimbolsInfo WHERE ";
            query += "ticker='" + ticker + "' and period='" + interval + "' and stock_id=" + stock_id.ToString() + " ";
 
            DbCommand command = _wrapper.create_command(_wrapper.create_query(query));
            command.Transaction = _wrapper.get_transaction(IsolationLevel.ReadCommitted);
 
            /*command.Parameters.Add(_wrapper.create_parameter("@ticker", ticker));
            command.Parameters.Add(_wrapper.create_parameter("@period", interval));
            command.Parameters.Add(_wrapper.create_parameter("@stock_id", stock_id));*/
 
            DbDataReader reader = command.ExecuteReader();
            while (reader.Read())
            {
                if (!reader.IsDBNull(3)) _beg_datetime = reader.GetDateTime(3);
                if (reader.IsDBNull(0))
                {
                    _bars_count = 0;
                    break;
                }
                _bars_count = reader.GetInt32(0);
                _beg_date_loaded = reader.GetDateTime(1);
                _end_date_loaded = reader.GetDateTime(2);
            }
 
            reader.Close();
            command.Transaction.Commit();
        }

command.Transaction = _wrapper.get_transaction(IsolationLevel.ReadCommitted);