Can I know how many remaining storage space in the phone when the app was installed to SD?

Question

If my app was installed to SD by user, and in Storage Sense, pictures, music, videos, apps and even download stuff all were set to store in SD, can I know how many remaining storage space in the phone?

    private async void Button_Click(object sender, RoutedEventArgs e)
    {
        Debug.WriteLine("start time:" + DateTime.Now.ToString(@"yyyy-MM-dd HH:mm:ss:fff"));

        /* Install folder */
        StorageFolder installFolder = Windows.ApplicationModel.Package.Current.InstalledLocation;
        IReadOnlyList<StorageFolder> installFolderList = await installFolder.GetFoldersAsync();
        Debug.WriteLine("installFolderList:" + installFolderList.Count);
        IReadOnlyList<StorageFile> installFileList = await installFolder.GetFilesAsync();
        Debug.WriteLine("installFileList:" + installFileList.Count);
        ulong installSize = await GetFreeSpace(installFolder);
        Debug.WriteLine("installSize:" + installSize / 1024 / 1024 / 1024);

        /* Local folder */
        StorageFolder localFolder = ApplicationData.Current.LocalFolder;
        IReadOnlyList<StorageFolder> localFolderList = await localFolder.GetFoldersAsync();
        Debug.WriteLine("localFolderList:" + localFolderList.Count);
        IReadOnlyList<StorageFile> localFileList = await localFolder.GetFilesAsync();
        Debug.WriteLine("localFileList:" + localFileList.Count);
        ulong localSize = await GetFreeSpace(localFolder);
        Debug.WriteLine("localSize:" + localSize / 1024 / 1024 / 1024);

        /* Local cache folder */
        StorageFolder localCacheFolder = ApplicationData.Current.LocalCacheFolder;
        IReadOnlyList<StorageFolder> localCacheFolderList = await localCacheFolder.GetFoldersAsync();
        Debug.WriteLine("localCacheFolderList:" + localCacheFolderList.Count);
        IReadOnlyList<StorageFile> localCacheFileList = await localCacheFolder.GetFilesAsync();
        Debug.WriteLine("localCacheFileList:" + localCacheFileList.Count);
        ulong localCacheSize = await GetFreeSpace(localCacheFolder);
        Debug.WriteLine("localCacheSize:" + localCacheSize / 1024 / 1024 / 1024);

        /* Temporary folder */
        StorageFolder tempFolder = ApplicationData.Current.TemporaryFolder;
        IReadOnlyList<StorageFolder> tempFolderList = await tempFolder.GetFoldersAsync();
        Debug.WriteLine("tempFolderList:" + tempFolderList.Count);
        IReadOnlyList<StorageFile> tempFileList = await tempFolder.GetFilesAsync();
        Debug.WriteLine("tempFileList:" + tempFileList.Count);
        ulong tempSize = await GetFreeSpace(tempFolder);
        Debug.WriteLine("tempSize:" + tempSize / 1024 / 1024 / 1024);

        /* Picture folder */
        StorageFolder picFolder = KnownFolders.PicturesLibrary;
        IReadOnlyList<StorageFolder> picFolderList = await picFolder.GetFoldersAsync();
        Debug.WriteLine("picFolderList:" + picFolderList.Count);
        IReadOnlyList<StorageFile> picFileList = await picFolder.GetFilesAsync();
        Debug.WriteLine("picFileList:" + picFileList.Count);
        ulong picSize = await GetFreeSpace(picFolder);
        Debug.WriteLine("picSize:" + picSize / 1024 / 1024 / 1024);

        /* CameraRoll folder */
        StorageFolder cameraRollFolder = KnownFolders.CameraRoll;
        IReadOnlyList<StorageFolder> cameraRollFolderList = await cameraRollFolder.GetFoldersAsync();
        Debug.WriteLine("cameraRollFolderList:" + cameraRollFolderList.Count);
        IReadOnlyList<StorageFile> cameraRollFileList = await cameraRollFolder.GetFilesAsync();
        Debug.WriteLine("cameraRollFileList:" + cameraRollFileList.Count);
        ulong cameraRollSize = await GetFreeSpace(cameraRollFolder);
        Debug.WriteLine("cameraRollSize:" + cameraRollSize / 1024 / 1024 / 1024);

        /* Music folder */
        StorageFolder musicFolder = KnownFolders.MusicLibrary;
        IReadOnlyList<StorageFolder> musicFolderList = await musicFolder.GetFoldersAsync();
        Debug.WriteLine("musicFolderList:" + musicFolderList.Count);
        IReadOnlyList<StorageFile> musicFileList = await musicFolder.GetFilesAsync();
        Debug.WriteLine("musicFileList:" + musicFileList.Count);
        ulong musicSize = await GetFreeSpace(musicFolder);
        Debug.WriteLine("musicSize:" + musicSize / 1024 / 1024 / 1024);

        /* Videos folder */
        StorageFolder videosFolder = KnownFolders.VideosLibrary;
        IReadOnlyList<StorageFolder> videoFolderList = await videosFolder.GetFoldersAsync();
        Debug.WriteLine("videoFolderList:" + videoFolderList.Count);
        IReadOnlyList<StorageFile> videoFileList = await videosFolder.GetFilesAsync();
        Debug.WriteLine("videoFileList:" + videoFileList.Count);
        ulong videosSize = await GetFreeSpace(videosFolder);
        Debug.WriteLine("videosSize:" + videosSize / 1024 / 1024 / 1024);

        Debug.WriteLine("end time:" + DateTime.Now.ToString(@"yyyy-MM-dd HH:mm:ss:fff"));
    }

    public static async Task<ulong> GetFreeSpace(IStorageItem sf)
    {
        var properties = await sf.GetBasicPropertiesAsync();
        var filteredProperties = await properties.RetrievePropertiesAsync(new[] { "System.FreeSpace" });
        var freeSpace = filteredProperties["System.FreeSpace"];
        return (ulong)freeSpace;
    }

Answer 1

Making an answer from the comment above:

Enumerate the pictures library, there should be 2 CameraRoll folders one internal and one external. Use

StorageFolder.Path

and check if the path starts with C:\ to see if the folder is the internal or external one as shown here.