C# ConfigMan.cs

    public static class ConfigMan
    {
        public static string ReadKey(string key) {
            return ConfigurationManager.AppSettings[key];
        }
        public static void WriteKey(string key,string value)
        {
            var cfa = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
            cfa.AppSettings.Settings[key].Value = value;
            cfa.Save();
            ConfigurationManager.RefreshSection("appSettings");
        }
    }