How to Upload and download multiple files asynchronously

The DownloadFileAsync/DownloadFileCompleted members of WebClient use the Event-based Asynchronous Pattern. If you want to use async and await, you should be using the Task-based Asynchronous Pattern.

In this case, you should use the DownloadFileTaskAsync member, as such:

private async Task DownloadFileAsync(DocumentObject doc)
{
try
{
using (WebClient webClient = new WebClient())
{
string downloadToDirectory = @Resources.defaultDirectory + doc.docName;
webClient.Credentials = System.Net.CredentialCache.DefaultNetworkCredentials;
await webClient.DownloadFileTaskAsync(new Uri(doc.docUrl), @downloadToDirectory);
//Add them to the local
Context.listOfLocalDirectories.Add(downloadToDirectory);
}
}
catch (Exception)
{
Errors.printError("Failed to download File: " + doc.docName);
}
}
private async Task DownloadMultipleFilesAsync(List doclist)
{
await Task.WhenAll(doclist.Select(doc => DownloadFileAsync(doc)));
}

Please note that your Context.listOfLocalDirectories.Add and Errors.printError methods should be threadsafe.

3 Replies

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Rajanikant Hawaldar7y ago
Accepted answer
try this too https://www.google.com/amp/s/tahirnaushad.com/2017/08/28/uploaddownload-files-in-asp-net-core-2-0/amp/
+1
Akash Ghadage7y ago
The DownloadFileAsync/DownloadFileCompleted members of WebClient use the Event-based Asynchronous Pattern. If you want to use async and await, you should be using the Task-based Asynchronous Pattern.

In this case, you should use the DownloadFileTaskAsync member, as such:
private async Task DownloadFileAsync(DocumentObject doc)

        {

            try

            {

                using (WebClient webClient = new WebClient())

                {

                    string downloadToDirectory = @Resources.defaultDirectory + doc.docName;

                    webClient.Credentials = System.Net.CredentialCache.DefaultNetworkCredentials;

                    await webClient.DownloadFileTaskAsync(new Uri(doc.docUrl), @downloadToDirectory);



                    //Add them to the local

                    Context.listOfLocalDirectories.Add(downloadToDirectory);

                }

            }

            catch (Exception)

            {

                Errors.printError("Failed to download File: " + doc.docName);

            }

        }



        private async Task DownloadMultipleFilesAsync(List doclist)

        {

            await Task.WhenAll(doclist.Select(doc => DownloadFileAsync(doc)));

        }
Please note that your Context.listOfLocalDirectories.Add and Errors.printError methods should be threadsafe.
+1
Rajanikant Hawaldar7y ago
Hi Chittaranjan, try this https://dotnetriders.wordpress.com/articles/how-to-upload-and-download-files-asynchronously-using-asp-net-mvc-4-5/ https://www.c-sharpcorner.com/article/upload-download-files-in-asp-net-core-2-0/ Thanks
+1