public static void UpdateAppSettings(string settingKey, string settingValue)
{
System.Configuration.Configuration config =
ConfigurationManager.OpenExeConfiguration(
ConfigurationUserLevel.None);
AppSettingsSection asSection = config.AppSettings;
asSection.Settings.Remove(settingKey);
asSection.Settings.Add(settingKey, settingValue);
config.Save(ConfigurationSaveMode.Full);
}