关于app。config更新节点问题

Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
AppSettingsSection appSettings = (AppSettingsSection)config.GetSection(“appSettings”);
appSettings.Settings.Remove(“UdpServerIP”);
appSettings.Settings.Remove(“UdpServerPort”);
appSettings.Settings.Remove(“App_id”);
appSettings.Settings.Remove(“Login_name”);
appSettings.Settings.Remove(“Login_pwd”);
appSettings.Settings.Remove(“Login_type”);
appSettings.Settings.Remove(“SiteNoSNum”);
appSettings.Settings.Add(“UdpServerIP”, tbUdpServerIP.Text);
appSettings.Settings.Add(“UdpServerPort”, tbUdpServerPort.Text);
appSettings.Settings.Add(“App_id”, tbApp_id.Text);
appSettings.Settings.Add(“Login_name”, tbLogin_name.Text);
appSettings.Settings.Add(“Login_pwd”, tbLogin_pwd.Text);
appSettings.Settings.Add(“Login_type”, tbLogin_type.Text);
appSettings.Settings.Add(“SiteNoSNum”, ptModel.siteNoSNum);
config.Save();
ConfigurationManager.RefreshSection(“appSettings”);
为什么节点不更新，那地方写的有问题