/// <summary>
/// Preserves state associated with this page in case the application is suspended or the
/// page is discarded from the navigation cache. Values must conform to the serialization
/// requirements of <see cref="SuspensionManager.SessionState"/>.
/// </summary>
/// <param name="sender">The source of the event; typically <see cref="NavigationHelper"/></param>
/// <param name="e">Event data that provides an empty dictionary to be populated with
/// serializable state.</param>
private void navigationHelper_SaveState(object sender, SaveStateEventArgs e)
{
}
void navigationHelper_SaveState(object sender, SaveStateEventArgs e)
{
if (_userViewModel != null)
e.PageState["signInStatus"] = _userViewModel.SignedIn;
}