WebClient DownloadFileAsync - How can I display download speed to the user?

Question

That's pretty much the whole question in the title. I have a WPF C# Windows application, I download files for the user and now want to display the speed.

Solution 1

mWebClient.DownloadProgressChanged += (sender, e) => progressChanged(e.BytesReceived);
//...
DateTime lastUpdate;
long lastBytes = 0;

private void progressChanged(long bytes)
{
    if (lastBytes == 0)
    {
        lastUpdate = DateTime.Now;
        lastBytes = bytes;
        return;
    }

    var now = DateTime.Now;
    var timeSpan = now - lastUpdate;
    var bytesChange = bytes - lastBytes;
    var bytesPerSecond = bytesChange / timeSpan.Seconds;

    lastBytes = bytes;
    lastUpdate = now;
}

And do whatever you need with the bytesPerSecond variable.

Solution 2

We can do this easily by determining how many seconds have passed since the download is started. We can divide BytesReceived value from total seconds to get the speed. Take a look at the following code.

DateTime _startedAt;

WebClient webClient = new WebClient();

webClient.DownloadProgressChanged += OnDownloadProgressChanged;

webClient.DownloadFileAsync(new Uri("Download URL"), "Download Path")

private void OnDownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
{
    if (_startedAt == default(DateTime))
    {
        _startedAt = DateTime.Now;
    }
    else
    {
        var timeSpan = DateTime.Now - _startedAt;
        if (timeSpan.TotalSeconds > 0)
        {
            var bytesPerSecond = e.BytesReceived / (long) timeSpan.TotalSeconds;
        }
    }
}