AppSettings read write

AppSettings.cs

public static string GetSettings(string key)
        {
            return ConfigurationManager.AppSettings[key] ?? "";
        }

        public static void SetSetting(string key, string value)
        {
            Configuration configuration = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
            configuration.AppSettings.Settings[key].Value = value;
            configuration.Save();

            ConfigurationManager.RefreshSection("appSettings");
        }