metro 文本文件操作

private async void Mource_Move(object sender, RoutedEventArgs e)
        {
            StackPanel panel = (StackPanel)sender;
            TextBlock block = (TextBlock)panel.Children[1];
            string message = block.Text;

            var root = Windows.Storage.ApplicationData.Current.LocalFolder;
            var path = await root.CreateFolderAsync("fillf", CreationCollisionOption.OpenIfExists);
            var filename = await path.CreateFileAsync("aaa.txt", CreationCollisionOption.OpenIfExists);
            var _WriteThis = message;
            await Windows.Storage.FileIO.AppendTextAsync(filename, _WriteThis);
            //检验是否写入成功
            var _ReadThis = await Windows.Storage.FileIO.ReadTextAsync(filename);
            MessageDialog dialog = new MessageDialog(_ReadThis);
            dialog.ShowAsync();

        }