private async void CaptureBtn_Click(object sender, RoutedEventArgs e)
 {
            file = await ApplicationData.Current.LocalFolder.CreateFileAsync("AttendanceImage.jpg",CreationCollisionOption.ReplaceExisting);
            await mediaCapture.CapturePhotoToStorageFileAsync(Windows.Media.MediaProperties.ImageEncodingProperties.CreateJpeg(), file);
}