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我正在为自己开发一个应用程序，事实上这个应用程序是用于下载我们公司
在这个应用程序中使用的最新版本的防病毒软件我想使用DownloadFileAsync方法下载我的文件，但它不起作用，我收到了这个错误：

WebClient does not support concurrent I/O operations.

这是我的源代码：

private static WebClient wc = new WebClient();
        private static ManualResetEvent handle = new ManualResetEvent(true);
        private DateTime myDate = new DateTime();
        private void btn_test_Click(object sender, EventArgs e)
        {

            using (WebClient client = new WebClient())
            {
                client.Encoding = System.Text.Encoding.UTF8;
                var doc = new HtmlAgilityPack.HtmlDocument();
                ArrayList result = new ArrayList();
                doc.LoadHtml(client.DownloadString("https://www.symantec.com/security_response/definitions/download/detail.jsp?gid=savce"));
                foreach (var href in doc.DocumentNode.Descendants("a").Select(x => x.Attributes["href"]))
                {
                    if (href == null) continue;
                    string s = href.Value;
                    Match m = Regex.Match(s, @"http://definitions.symantec.com/defs/(\d{8}-\d{3}-v5i(32|64)\.exe)");
                    if (m.Success)
                    {
                        Match date = Regex.Match(m.Value, @"(\d{4})(\d{2})(\d{2})");
                        Match filename = Regex.Match(m.Value, @"\d{8}-\d{3}-v5i(32|64)\.exe");
                        int year = Int32.Parse(date.Groups[0].Value);
                        int month = Int32.Parse(date.Groups[1].Value);
                        int day = Int32.Parse(date.Groups[3].Value);

                        myDate = new DateTime(
                                Int32.Parse(date.Groups[1].Value),
                                Int32.Parse(date.Groups[2].Value),
                                Int32.Parse(date.Groups[3].Value));
                        listBox1.Items.Add(m.Value);
                        if (myDate == DateTime.Now)
                        {
                            Download(m.Value,filename.Value);

                        }
                        else
                        {
                            MessageBox.Show("There is no Update!");
                        }
                    }
                }

            }
        }
        private void Download(string url, string fileName)
        {
            wc.DownloadProgressChanged += new DownloadProgressChangedEventHandler(wc_DownloadProgressChanged);
            wc.DownloadFileAsync(new Uri(url), @"\\10.1.0.15\Symantec Update Weekly\\" + fileName);
            //wc.DownloadFile(url, @"\\10.1.0.15\Symantec Update Weekly\\" + fileName);
        }

        private void WcOnDownloadFileCompleted(object sender, AsyncCompletedEventArgs e)
        {
            if (!e.Cancelled && e.Error == null)
            {
                //async download completed successfully
            }
            handle.Set();
        }

        private void wc_DownloadProgressChanged(object sender, System.Net.DownloadProgressChangedEventArgs e)
        {
            double bytesIn = double.Parse(e.BytesReceived.ToString());
            double totalBytes = double.Parse(e.TotalBytesToReceive.ToString());
            double percentage = bytesIn / totalBytes * 100;
            progressBar1.Value = int.Parse(Math.Truncate(percentage).ToString());
        }

当我的应用程序尝试下载文件时
，上述方法似乎无法同时下载多个文件。
我搜索了很多并找到了这个解决方案，但我无法将它应用到我的应用程序中。
我该如何解决。
谢谢你的建议。

4

1 回答 1

3 
// Declare a field to hold the Task
private static Task DownloadTask;

private Task Download(string url, string fileName)
{
    var wc = new WebClient();
    wc.DownloadProgressChanged += new DownloadProgressChangedEventHandler(wc_DownloadProgressChanged);
    return wc.DownloadFileTaskAsync(new Uri(url), @"\\10.1.0.15\Symantec Update Weekly\\" + fileName);
}

您可能需要更改进度条来处理多个线程。

里面btn_test_Click

// Before foreach
var tasks = new List<Task>();

// Inside foreach
if (myDate == DateTime.Now)
{
    MessageBox.Show("Updates are New");
}
else
{
    tasks.Add(Download(m.Value,filename.Value));
}

// After foreach
// You can also set the TimeSpan value and update the progressbar
// periodically until all the tasks are finished
DownloadTask = Task.WhenAll(tasks);

见Task.WaitAll，WebClient.DownloadFileTaskAsync

于 2013-06-12T13:11:57.187 回答