如何从postgres表中获取数据，并以编程方式从C#中将其作为插入查询存储在文件中？

using System;
using System.IO;
using Npgsql;

public class Program
{
    public static void Main()
    {
        string connectionString = "Host=<hostname>;Port=<port>;Database=<database>;Username=<username>;Password=<password>";
        string query = "SELECT * FROM <table>";

        using (NpgsqlConnection connection = new NpgsqlConnection(connectionString))
        {
            connection.Open();

            using (NpgsqlCommand command = new NpgsqlCommand(query, connection))
            {
                using (NpgsqlDataReader reader = command.ExecuteReader())
                {
                    using (StreamWriter writer = new StreamWriter("output.txt"))
                    {
                        while (reader.Read())
                        {
                            // 根据表结构读取数据
                            int id = reader.GetInt32(0);
                            string name = reader.GetString(1);
                            // ...

                            // 将数据写入文件
                            writer.WriteLine($"ID: {id}, Name: {name}");
                        }
                    }
                }
            }
        }

        Console.WriteLine("数据已存储在文件中。");
    }
}