每次下载一个文件

本文关键字：一个 文件 下载 | 更新日期: 2023-09-27 18:03:53

我有foreach，它解析出文件URL。在每个循环结束时，我想下载文件，但是，就像我现在拥有的那样，它下载了所有文件。我需要弄清楚如何阻止UI线程(其中有foreach)，而下载完成。

我现在的情况:

foreach (... in ...)
{
  //some code that extracts FileURL and fileName
  downloadFile(FileURL, fileName)
  //should wait here, without blocking UI
  //are.WaitOne(); //this blocks the UI
}
AutoResetEvent are = new AutoResetEvent(false);
void downloadFile(String FileURL, String fileName)
{
  Thread bgThread = new Thread(() =>
  {
    WebClient FileClient = new WebClient();
    FileClient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(FileClient_DownloadProgressChanged);
    FileClient.DownloadFileCompleted += new AsyncCompletedEventHandler(FileClient_DownloadFileCompleted);
    FileClient.DownloadFileAsync(new Uri(FileURL), fileName);
  //should wait here, without blocking UI
  //are.WaitOne(); //this either downloads one, or both in paralel.
  });
  bgThread.Start();
}
void FileClient_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
{
  this.BeginInvoke((MethodInvoker)delegate
  {
    label5.Text = String.Format("Downloaded {0} of {1} bytes...", e.BytesReceived.ToString(), e.TotalBytesToReceive.ToString());
    progressBar1.Value = e.ProgressPercentage;
  });
}
void FileClient_DownloadFileCompleted(object sender, AsyncCompletedEventArgs e)
{
  this.BeginInvoke((MethodInvoker)delegate
  {
    label5.Text = "Done.";
    //stop the waiting
    are.Set();
  });
}

所以，有没有办法等待UI线程，而下载文件同步完成，然后继续我的大foreach?

每次下载一个文件

你可以这样做:

List<Task> tasks = new List<Task>();
foreach(....)
{
Thread bgThread = new Thread(() =>
  {
    WebClient FileClient = new WebClient();
    FileClient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(FileClient_DownloadProgressChanged);
    FileClient.DownloadFileCompleted += new AsyncCompletedEventHandler(FileClient_DownloadFileCompleted);
    FileClient.DownloadFileAsync(new Uri(FileURL), fileName);
  //should wait here, without blocking UI
  //are.WaitOne(); //this either downloads one, or both in paralel.
  });
  bgThread.Start();
    tasks.Add(bgThread);

}
var arr = tasks.ToArray();
Task.WaitAll(arr);
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