public static string GetAppSettingsValue(string key) {     ConfigurationManager.RefreshSection("appSettings");     return ConfigurationManager.AppSettings[key] ?? string.Empty; } public static bool UpdateAppSettings(string key, string value) {     var _config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);     if (!_config.HasFile)     {  throw new ArgumentException("程序配置文件缺失！");     }     KeyValueConfigurationElement _key = _config.AppSettings.Settings[key];     if (_key == null)  _config.AppSettings.Settings.Add(key, value);     else  _config.AppSettings.Settings[key].Value = value;     _config.Save(ConfigurationSaveMode.Modified);     return true; }