var picker = new FileOpenPicker();
picker.SuggestedStartLocation = PickerLocationId.PicturesLibrary;
picker.ViewMode = PickerViewMode.Thumbnail;
picker.FileTypeFilter.Add(".jpg");
picker.FileTypeFilter.Add(".jpeg");

var file = await picker.PickSingleFileAsync();
var stream = await file.OpenAsync(FileAccessMode.Read);
var jpegInfo = ExifReader.ReadJpeg(stream.AsStream());

private void Button_Click(object sender, RoutedEventArgs e)
{
  var task = new PhotoChooserTask();
  task.Completed += task_Completed;
  task.Show();
}

void task_Completed(object sender, PhotoResult e)
{
  var jpeginfo = ExifReader.ReadJpeg(e.ChosenPhoto);
  this.DataContext = jpeginfo;
}