//获取Configuration对象

            Configuration config = System.Configuration.ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);

            //根据Key读取<add>元素的Value

            string name = config.AppSettings.Settings["name"].Value;

            //写入<add>元素的Value

            config.AppSettings.Settings["name"].Value = "fx163";

            //增加<add>元素

            config.AppSettings.Settings.Add("url", "http://www.fx163.net");

            config.AppSettings.Settings.Add("url2", "http://www.fx163.net");

            //删除<add>元素

            config.AppSettings.Settings.Remove("url2");

            //一定要记得保存，写不带参数的config.Save()也可以

            config.Save(ConfigurationSaveMode.Modified);

            //刷新，否则程序读取的还是之前的值（可能已装入内存）

            System.Configuration.ConfigurationManager.RefreshSection("appSettings");