数组 。数据集？？？

Question

我想把读取出来的字段存到数组里（string [] a）应该怎么做

public string  QeryList()
        {
            string str = " ";
            string qery = "SELECT Nums from orderList ";
            SqlDataReader reader = DBHelper.GetReadData(qery);

            if (reader.HasRows)
            { reader.Read();
                   str += "\n 数量："+reader["Nums"].ToString();

                }
                     return str;

        }