using System;
using System.Configuration;

class Program
{
    static void Main()
    {
        // 读取初始连接字符串
        string connectionString = ConfigurationManager.ConnectionStrings["MyConnectionString"].ConnectionString;
        Console.WriteLine("Initial Connection String: " + connectionString);

        // 更改连接字符串（示例）
        connectionString = "Data Source=newServer;Initial Catalog=newDatabase;User ID=newUser;Password=newPassword;";
        UpdateConnectionStringInConfig(connectionString);

        // 重新读取更新后的连接字符串
        connectionString = ConfigurationManager.ConnectionStrings["MyConnectionString"].ConnectionString;
        Console.WriteLine("Updated Connection String: " + connectionString);
    }

    static void UpdateConnectionStringInConfig(string newConnectionString)
    {
        // 更新配置文件中的连接字符串
        var config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
        var connectionStringSettings = new ConnectionStringSettings("MyConnectionString", newConnectionString);
        config.ConnectionStrings.ConnectionStrings.Remove(connectionStringSettings);
        config.ConnectionStrings.ConnectionStrings.Add(connectionStringSettings);
        config.Save(ConfigurationSaveMode.Modified);
        ConfigurationManager.RefreshSection("connectionStrings");
    }
}