WebClient does not support concurrent I/O operations

Question

How can I get this error from with in the DownloadStringCompleted Event? Doesn\'t that mean, it\'s finished? Is there another event I can fire this from?

I get this

Answer 1

Instead of using WebClient use HttpClient to do parallel HTTP calls. Below code shows how to download files.

        HttpClient httpClient = new HttpClient();
        var documentList=_documentManager.GetAllDocuments();
        documentList.AsParallel().ForAll(doc =>
        {

            var responseResult= httpClient.GetAsync(doc.FileURLPath);
            using (var memStream = responseResult.Result.Content.ReadAsStreamAsync().Result)
            {
                using (var fileStream =File.Create($"{filePath}\\{doc.FileName}"))
                {
                    memStream.CopyTo(fileStream);
                }

            }
        });