使用C#查询MySQL时报“给定键不在字典中”错误的求助

我们维护的系统基于旧版本.NET Framework（版本：4.0.30319.42000），测试时安装了MySql.Data.6.10.9包。示例程序可成功连接至MySQL v8.0.32，但执行select version();时触发错误：执行查询出错: The given key was not present in the dictionary.

测试输出 #

.Net版本: 4.0.30319.42000
尝试打开连接...
连接成功！
执行查询出错: The given key was not present in the dictionary.
Press any key to continue . . .

已尝试的连接字符串 #

• server=192.168.56.5;uid=root;port=3306;database=test-source;pwd=mysql_root_password
• server=192.168.56.5;uid=root;port=3306;database=test-source;charset=utf8mb4;pwd=mysql_root_password

两种连接字符串均出现相同错误，此前参考的调整连接字符集的方案无效，希望排查是否有遗漏的解决点。

完整示例代码 #

using System;
using MySql.Data.MySqlClient;

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine(".Net版本: " + Environment.Version.ToString());
        string connectionString = "server=192.168.56.5;uid=root;port=3306;database=test-source;pwd=mysql_root_password";

        try
        {
            using (var connection = new MySqlConnection(connectionString))
            {
                Console.WriteLine("尝试打开连接...");
                connection.Open();

                if (connection.State == System.Data.ConnectionState.Open)
                {
                    Console.WriteLine("连接成功！");

                    // 获取MySQL版本
                    try
                    {
                        string query = "SELECT VERSION();";
                        using (var command = new MySqlCommand(query, connection))
                        {
                            string version = command.ExecuteScalar().ToString();
                            Console.WriteLine("MySQL版本: " + version);
                        }
                    }
                    catch (Exception ex)
                    {
                        Console.WriteLine("执行查询出错: " + ex.Message);
                    }

                }
                else
                {
                    Console.WriteLine("连接打开失败。");
                }
            }
        }
        catch (MySqlException ex)
        {
            Console.WriteLine("MySQL异常: " + ex.Message);
        }
        catch (Exception ex)
        {
            Console.WriteLine("通用异常: " + ex.Message);
        }
    }
}

内容的提问来源于Stack Exchange，提问作者Mike