如何附加一个文件，在异步的Windows Phone 8

我想追加到最新的Windows Phone的文件。问题是我想要做异步的一切，我不知道该怎么做。

I'm trying to append to a file in the latest Windows Phone. The problem is i'm trying to do everything asynchronously and i'm not sure how to do it.

    private async void writeResult(double lat, double lng)
    {

        StorageFolder localFolder = ApplicationData.Current.LocalFolder;
        StorageFile storageFile = await localFolder.CreateFileAsync("result.txt", CreationCollisionOption.OpenIfExists);
        Stream writeStream = await storageFile.OpenStreamForWriteAsync();
        using (StreamWriter writer = new StreamWriter(writeStream))
        //using (StreamWriter sw = new StreamWriter("result.txt", true))
        {
            {
                await writer.WriteLineAsync(lat + "," + lng);
                //await sw.WriteLineAsync(lat + "," + lng);
                writer.Close();
                //sw.Close();
            }
        }
    }

我有这到目前为止，其写入文件很好，我可以读取它以后大同小异，但它在写我有什么，而不是在新的一行。该注释掉行显示如何去无WP7流，但我不能得到那个工作是（真正的意思是附加标志）和真的应该被无论如何利用新的WP8方法。

I have this so far, which writes to the file fine and I can read it later on much the same, however it writes over what I have instead of on a new line. The commented out lines show how to go about without the stream in WP7, but I can't get that to work either (the true is is the append flag) and really should be utilizing the new WP8 methods anyway.

任何意见AP preciated

Any comments appreciated