[Solved] AWAIT multiple file downloads with DownloadDataAsync

by


  • First, you tagged your question with async-await without actually using it. There really is no reason anymore to use the old asynchronous paradigms.
  • To wait asynchronously for all concurrent async operation to complete you should use Task.WhenAll which means that you need to keep all the tasks in some construct (i.e. dictionary) before actually extracting their results.
  • At the end, when you have all the results in hand you just create the new result dictionary by parsing the uri into the file name, and extracting the result out of the async tasks.
async Task<Dictionary<string, byte[]>> ReturnFileData(IEnumerable<string> urls)
{
    var dictionary = urls.ToDictionary(
        url => new Uri(url),
        url => new WebClient().DownloadDataTaskAsync(url));

    await Task.WhenAll(dictionary.Values);

    return dictionary.ToDictionary(
        pair => Path.GetFileName(pair.Key.LocalPath),
        pair => pair.Value.Result);
}

5

solved AWAIT multiple file downloads with DownloadDataAsync