Process download data asynchronous

Question

Is there an easy method to process the loaded data while the download is still running? I do not want to wait for the download to finish to have the whole data on memory or disk before processing. I want to do this because my data is compressed, and I'd like to decompress the byte packets on the run and write them then directly onto disk. So that I never use more memory than one download packet.

I tried to get along with the WebClient class but I didn't find out how to access the last loaded bytes in the DownloadProgressChanged event.

Something like this:

WebClient wc = new WebClient();
Uri uri = new Uri(myURL);
wc.DownloadProgressChanged += wc_DownloadProgressChanged;
wc.DownloadDataAsync(uri);

...

void wc_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
{
    ProcessData(e.Bytes,e.BytesReceived); //e.Bytes should access the downloaded byte packet
    //but it doesn't exist
}

I figured it already out using libcurl, but I'd like to know if it's possible without using external libraries.

Answer 1

Haven't had the possibility to test it but it could work something like this:

    public void DownloadFileAsync()
    {
        WebClient wc = new WebClient();
        Uri uri = new Uri(myURL);
        //Open Stream from URI
        wc.OpenReadCompleted += new OpenReadCompletedEventHandler(OpenReadCallback);
        wc.OpenReadAsync(uri);
    }


    private static void OpenReadCallback(Object sender, OpenReadCompletedEventArgs e)
    {
        Stream resStream = null;

        try
        {
            resStream = (Stream)e.Result;
            //Your decompression stream Gzip for example
            using (GZipStream compressionStream = new GZipStream(resStream, CompressionMode.Decompress))
            {
                //write gzip stream to file
                using (
                    FileStream outFile = new FileStream(@"c:\mytarget.somefile", FileMode.Create, FileAccess.Write,
                        FileShare.None))
                      compressionStream.CopyTo(outFile);
            }
        }
        finally
        {
            if (resStream != null)
            {
                resStream.Close();
            }
        }
    }