Windows Store apps, download multiple files with streams

I have the following method that I am using to download the content of a file:

public async Task<String> DownloadFileService(String filePath, string id)
{
    string resposta = string.Empty;
    try
    {
        using (var httpClient = new HttpClient { BaseAddress = Constants.baseAddress })
        {
            string token = App.Current.Resources["token"] as string;
            httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);

            string fname = Path.GetFileName(filePath);
            string path = Path.GetDirectoryName(filePath);
            path = path.Replace(fname, "");
            StorageFolder folder = await ApplicationData.Current.LocalFolder.CreateFolderAsync(Constants.DataDirectory + "\\" + path, CreationCollisionOption.OpenIfExists);

            StorageFile imgFile = await folder.CreateFileAsync(fname, CreationCollisionOption.ReplaceExisting);

            using (var response2 = await httpClient.GetAsync("file?fileId=" + id))
            {

                Stream imageStream = await response2.Content.ReadAsStreamAsync();
                byte[] bytes = new byte[imageStream.Length];

                imageStream.Read(bytes, 0, (int)imageStream.Length);


                await FileIO.WriteBytesAsync(imgFile, bytes);
                resposta = Convert.ToBase64String(bytes);
            }

        }
        return resposta;
    }
    catch (Exception e)
    {
        Debug.WriteLine(e.Message);
    }
}

      

        
        
        
      

    

I would like to know how can I call this multiple times to download multiple files at the same time and wait for all files to download and then do other things.

EDIT

After that, I tried to create the following method:

public async void checkFilesExist(JsonArray array, string path)
{
    List<Document> list = new List<Document>();
    ObjectsService obj = new ObjectsService();
    List<Task> ts = new List<Task>();

    foreach (var item in array)
    {
        JsonObject newDoc;
        JsonObject.TryParse(item.Stringify(), out newDoc);

        if (newDoc.ContainsKey("libraryType") || !newDoc.ContainsKey("fileName"))
            continue;
        string name = newDoc["fileName"].GetString();
        string id = newDoc["_id"].GetString();
        File file = new File(name);
        file.id = id;
        Document doc = file;
        doc.Parent = Document.FromPath(path);

        path = path.Replace("/", "\\");
        StorageFolder folder = await ApplicationData.Current.LocalFolder.CreateFolderAsync(Constants.DataDirectory + "\\" + path, CreationCollisionOption.OpenIfExists);
        try
        {
            await folder.GetFileAsync(file.Name);
        }
        catch (Exception e)
        {
            list.Add(doc);
            Task x = obj.DownloadFileService(doc.GetFullPath(), file.id);
            ts.Add(x);
            Debug.WriteLine(" Ex: " + e.Message);
        }
    }
    try
    {
        Task.WaitAll(ts.ToArray());
        Debug.WriteLine("AFTER THrEADS");
    }
    catch (Exception e)
    {
        Debug.WriteLine("Ex2:  " + e.Message);
    }
}

      

        
        
        
      

    

What is it, with the response in json I get from the webservice an enumeration of some files, I check if they already exist in the local folder. If they don't, I will call the method I had when I started the question.

Then I have a task list and I add the call DownloadFileService()

as a new task in the list, after which I do Task.WaitAll()

to wait for the download to complete.

With fiddler I can see that all the downloads start, but for some reason my code doesn't stop at Task.WaitAll()

, it just keeps running and it starts using files that are still downloading, creating a bunch of problems: D