c#公共类获取当前页面

c#公共类的时候，没法导航的问题，解决方法：

 private static PhoneApplicationFrame _frame;

      private static PhoneApplicationFrame Frame { get
      {
          return _frame ?? (_frame = (PhoneApplicationFrame) Application.Current.RootVisual);
      } }

    Deployment.Current.Dispatcher.BeginInvoke(() =>
          {
              if (MessageBox.Show(message.ToString(), "", MessageBoxButton.OKCancel) == MessageBoxResult.OK)
                  Frame.Navigate(new Uri(url, UriKind.Relative));
          });