private static async Task<StorageFile> TakePhotoAsync(string filename)
{
StorageFile photoFile = await KnownFolders.PicturesLibrary.CreateFileAsync(
filename, CreationCollisionOption.GenerateUniqueName);
ImageEncodingProperties imageProperties = ImageEncodingProperties.CreateJpeg();
await mediaCapture.CapturePhotoToStorageFileAsync(imageProperties, photoFile);
return photoFile;
}