Modify Running App Config

file.cs

var config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
config.AppSettings.Settings.Remove("CurrentUICulture");
config.AppSettings.Settings.Add("CurrentUICulture", name);
config.Save(ConfigurationSaveMode.Modified, true);
// Force a reload of a changed section.
ConfigurationManager.RefreshSection("appSettings");