Question

在form1的顶部

Stopwatch sw = new Stopwatch();

然后

private void btnDownload_Click(object sender, EventArgs e)
        {
            //urll.Add("http://download.thinkbroadband.com/1GB.zip");

            label7.Text = "Downloading images";

            var v = lines.Where(s => s.Contains("Name")).Select(s => s.Substring(15));
            var q = lines.Where(s => s.Contains("Code")).Select(s => s.Substring(15));
            var r = q.Where(c => c == "is").Concat(q.Where(c => c != "is"));
            var p = v.Where(c => c == "Israel").Concat(v.Where(c => c != "Israel"));
            var n = r.Count();
            int i = 0;

            var results = p.ToList();

            downloadFile(ExtractImages.imagesUrls);
        }

        private Queue<string> _downloadUrls = new Queue<string>();

        private async void downloadFile(IEnumerable<string> urls)
        {
            foreach (var url in urls)
            {
                _downloadUrls.Enqueue(url);
            }

            await DownloadFile();
        }

        private async Task DownloadFile()
        {
            if (_downloadUrls.Any())
            {
                WebClient client = new WebClient();
                client.DownloadProgressChanged += ProgressChanged;
                client.DownloadFileCompleted += Completed;

                var url = _downloadUrls.Dequeue();

                await client.DownloadFileTaskAsync(new Uri(url), @"C:\Temp\TestingSatelliteImagesDownload\" + count + ".jpg");
                return;
            }
        }

        private void ProgressChanged(object sender, DownloadProgressChangedEventArgs e)
        {
            // Calculate download speed and output it to labelSpeed.
            label3.Text = string.Format("{0} kb/s", (e.BytesReceived / 1024d / sw.Elapsed.TotalSeconds).ToString("0.00"));
        }

已完成的活动

long bytesFromCompletedFiles = 0;
        // The event that will trigger when the WebClient is completed
        private async void Completed(object sender, AsyncCompletedEventArgs e)
        {
            if (e.Cancelled == true)
            {
                MessageBox.Show("Download has been canceled.");
            }
            else
            {
                ProgressBar1.Value = 100;
                count++;
                bytesFromCompletedFiles += totalBytes[count -1];
                await DownloadFile();
            }
        }

问题是我从不启动sw（秒表）并且从不在任何地方停止/重置它。所以在行：

label3.Text = string.Format("{0} kb/s", (e.BytesReceived / 1024d / sw.Elapsed.TotalSeconds).ToString("0.00"));

我在sw上看到无限的标志

问题是我应该在哪里开始/停止/重置sw？

现在，当我正在运行程序时，我没有在label3上看到任何内容，我猜是因为无限，而且我没有启动sw（秒表）。

Answer 1

在您开始下载之前启动Stopwatch是有意义的，因为如果您提前启动它会产生错误的结果

private async Task DownloadFile()
{
    if (_downloadUrls.Any())
    {
        WebClient client = new WebClient();
        [...]

        sw = Stopwatch.StartNew();
        await client.DownloadFileTaskAsync(new Uri(url), @"C:\Temp\TestingSatelliteImagesDownload\" + count + ".jpg");
        return;
    }
}

在下载取消或完成下载后停止

// The event that will trigger when the WebClient is completed
private async void Completed(object sender, AsyncCompletedEventArgs e)
{
    if ([...])
    {
        [...]
    }
    else
    {
        [...]
    }
    sw.Stop();
}

我应该如何使用秒表来计算文件下载的下载速度？

1 个答案: