在C#中以编程方式从app.config访问system.net设置

using System;
using System.Configuration;

namespace ReadAppConfig
{
    class Program
    {
        static void Main(string[] args)
        {
            // 读取app.config中的system.net设置
            string defaultProxy = ConfigurationManager.AppSettings["system.net/defaultProxy"];
            Console.WriteLine($"Default Proxy: {defaultProxy}");

            // 修改app.config中的system.net设置
            Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
            config.AppSettings.Settings["system.net/defaultProxy"].Value = "New Proxy Value";
            config.Save(ConfigurationSaveMode.Modified);
            ConfigurationManager.RefreshSection("appSettings");

            // 读取修改后的app.config中的system.net设置
            defaultProxy = ConfigurationManager.AppSettings["system.net/defaultProxy"];
            Console.WriteLine($"Default Proxy (after modification): {defaultProxy}");
        }
    }
}