c# - 如何给下载器添加停止按钮

Question

我正在为我的应用程序开发一个下载器管理器，但我不知道如何使“停止”按钮起作用我正在搜索解决方案，但我找不到任何可以帮助我的东西代码是[c#]

private void btnDownload_Click(object sender, EventArgs e)
{
  btnDownload.Enabled = false;
  btnStop.Enabled = true;
  WebClient webClient = new WebClient();
  webClient.DownloadFileCompleted += new AsyncCompletedEventHandler(Completed);
  webClient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(ProgressChanged);
webClient.DownloadFileAsync(new Uri(url.Text), path.Text ; )
}

private void ProgressChanged(object sender, DownloadProgressChangedEventArgs e)
    {
  progressBar.Value = e.ProgressPercentage;
}

private void Completed(object sender, AsyncCompletedEventArgs e)
{
  MessageBox.Show("Download completed!");
}

private void btnstop (object sender , e)
{
  btnDownload.Enabled = true;
  btnstop.Enabled = false;
  progressbar.value = 0;   
}

Answer 1

作为Nitro.de说，你应该使用 WebClient.CancelAsync .

Cancels a pending asynchronous operation.

并记住检查 e.Cancelled 是否为真

private void Completed(object sender, AsyncCompletedEventArgs e)
{
    if(e.Cancelled)
        MessageBox.Show("Download cancelled!");
    else
        MessageBox.Show("Download completed!");
}