Silverlight windows phone 8.1 FileOpenPicker for all files Continue not working

i create silverlight windows phone 8.1 project and i need to choose all kind of file from windows phone

i used FileOpenPicker for choose the file it redirect correctly and i can choose the file this is my code

       FileOpenPicker openPicker = new FileOpenPicker();
        openPicker.ViewMode = PickerViewMode.List;
        openPicker.SuggestedStartLocation = PickerLocationId.DocumentsLibrary;

        openPicker.FileTypeFilter.Add("*");
        openPicker.PickMultipleFilesAndContinue();

And i follow this msdn for receiving select

In my case if i selecting file and come back to the app its every thing working if i without select any file and come back using mobile hardware back button my app come to home screen. but it need to stay file picker page

my first page

when i press mobile hardware back button in above screen the page redirect to my first page it need to stay in my second page

thanks

Finally i got the answer and avoid redirection

 bool reset;
        protected override void OnNavigatingFrom(NavigatingCancelEventArgs e)
        {

            if(reset && e.uri.tostring().Equals("MainPage.xaml"))
             {
                e.Cancel = true;
                reset = false
             }


        }
        protected override void OnNavigatedTo(NavigationEventArgs e)
        {

            reset = e.NavigationMode == NavigationMode.Reset;
        }