c# - 如何创建将结果返回到文本文件的 MySql 数据库连接？

Question

我想编写一条 MySql 语句，该语句将连接到数据库，从表中选择一列，然后将该数据输出到计算机上特定位置的文本文件中。我已经在互联网上搜索了几天，似乎没有找到我正在寻找的答案。我对 C#、MySql 和 Visual Studio 相当陌生。我只是想学习如何写出正确的陈述并获得想要的结果。任何帮助将不胜感激。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using MySql.Data.MySqlClient;
using MySql.Data;
using System.Windows.Forms;
using System.IO;

namespace NewPractice
{
    public class Connect
    {
        static void Main()
        {
            string results = @"server=111.111.11.111; userid=anyone;
                password=anypassword; database=anydatabase";    
            MySqlConnection conn = null;

            try
            {
                conn = new MySqlConnection(results);
                conn.Open();
                //Console.WriteLine(
                File.WriteAllLines(
                    @"C:\Documents and Settings\anyone\My Documents\Tests\testoutput.txt", 
                    results.ToArray());
            }
            catch (MySqlException ex)
            {
                Console.WriteLine("Error: (0)", ex.ToString());
            }
            finally
            {
                if (conn != null)
                {
                    conn.Close();
                }
            }
        }      
    }
}

Answer 1

您正在将结果字符串的内容写入文件，而不是您尝试选择的数据。您需要运行 sql 命令并获取 SqlDataReader 对象以将数据写入文件。

string results = @"server=111.111.11.111; userid=anyone; 
    password=anypassword; database=anydatabase";

MySqlConnection connection = new MySqlConnection(results);
MySqlCommand command = connection.CreateCommand();
MySqlDataReader reader;
command.CommandText = "select * from mycustomers";
connection.Open();
reader = command.ExecuteReader();
using(var sw = new StreamWriter("C:\MyPath\MyFile.txt"))
{
    while (reader.Read())
    {
        var row = (IDataRecord)reader;
        sw.WriteLine(row["myColumn"]);
    }
}
connection.Close();