var photoChooserTask = new PhotoChooserTask();
photoChooserTask.Completed += photoChooserTask_Completed;
photoChooserTask.Show();

public FileOpenPickerContinuationEventArgs FileOpenPickerContinuationArgs { get; set; }
private void Application_ContractActivated(object sender, IActivatedEventArgs e)
{
    var fileOpenPickerContinuationArgs = e as FileOpenPickerContinuationEventArgs;
    if (fileOpenPickerContinuationArgs != null)
    {
this.FileOpenPickerContinuationArgs =      fileOpenPickerContinuationArgs;
    }
}

void Button_Click(object sender, RoutedEventArgs e)
{
    var op = new FileOpenPicker();
    
    op.ContinuationData["Operation"] = "LoadPicture";
    op.FileTypeFilter.Add(".jpg");
    op.FileTypeFilter.Add(".png");
    op.PickSingleFileAndContinue();
}

protected override void OnNavigatedTo(NavigationEventArgs e)
{
    base.OnNavigatedTo(e);

    var app = App.Current as App;
    if (app.FileOpenPickerContinuationArgs != null)
    {
      this.ContinueFileOpenPicker(app.FileOpenPickerContinuationArgs);
    }
}

async void ContinueFileOpenPicker(FileOpenPickerContinuationEventArgs args)
{
    if ((args.ContinuationData["Operation"] as string) == "LoadPicture"
        && args.Files.Count > 0)
    {

        var imgFile = args.Files[0];

        var stream = (IRandomAccessStream)await imgFile.OpenAsync(FileAccessMode.Read);

        var bitmapImage = new BitmapImage();
        bitmapImage.SetSource(stream);
        this.MonImage.Source = bitmapImage;
    }
}

protected override void OnActivated(IActivatedEventArgs args)
        {
            base.OnActivated(args);

            var rootFrame = Window.Current.Content as Frame;
            var mainPage = rootFrame.Content as MainPage;
            if (mainPage != null && args is FileOpenPickerContinuationEventArgs)
            {
                mainPage.ContinueFileOpenPicker(args as FileOpenPickerContinuationEventArgs);
            }
        }

public sealed partial class MainPage : Page, IFileOpenPickerContinuable