private static void OnSaveSettingsCanExecuted(object sender, CanExecuteRoutedEventArgs e)
 {
     e.CanExecute = String.IsNullOrWhiteSpace(e.ExtractDataContext<IDataErrorInfo>().Error);
 }
 private static void OnSaveAsCanExecute(object sender, CanExecuteRoutedEventArgs e)
 {
     e.CanExecute = e.ExtractDataContext<ClearMineViewModel>().Game.GameState == GameState.Started;
 }