The SecondPage class subscribes to multiple ScriptNotify Events causing multiple page navigations

[AweHellYeah]

See this forum post on MSDN:
https://social.msdn.microsoft.com/Forums/windowsapps/en-US/8c08ecf9-7e70-4e04-9d0b-8ef6ec21e9c4/save-page-state-problem?forum=winappswithcsharp

To fix, unsubscribe to the ScriptNotify event in OnNavigatedFrom()

    protected override void OnNavigatedFrom(NavigationEventArgs e)
    {
        MyWebView.ScriptNotify -= Handle_ScriptNotify;
        base.OnNavigatedFrom(e);
    }