c# - 在“await DownloadTaskAsync”上调用WebClient.CancelAsync时出现WebException

这工作正常：

private WebClient _webClient;

private void ButtonStart_Click(object sender, RoutedEventArgs e) {
    using (_webClient = new WebClient()) {
        _webClient.DownloadFileTaskAsync("https://speed.hetzner.de/100MB.bin", @"D:\100MB.bin");
    }
}

private void ButtonStop_Click(object sender, RoutedEventArgs e) {
    _webClient.CancelAsync();
}

虽然这段代码（注意异步/等待模式）...：

private WebClient _webClient;

private async void ButtonStart_Click(object sender, RoutedEventArgs e) {
    using (_webClient = new WebClient()) {
        await _webClient.DownloadFileTaskAsync("https://speed.hetzner.de/100MB.bin", @"D:\100MB.bin");
    }
}

private void ButtonStop_Click(object sender, RoutedEventArgs e) {
    _webClient.CancelAsync();
}

...引发以下异常：


  System.Net.WebException
  
  该请求被中止：该请求被取消。

   at System.Net.ConnectStream.EndRead(IAsyncResult asyncResult)
   at System.Net.WebClient.DownloadBitsReadCallbackState(DownloadBitsState state, IAsyncResult result)
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.GetResult()
   at WpfApp1.MainWindow.<ButtonStart_Click>d__2.MoveNext() in WpfApp1\MainWindow.xaml.cs:line 19

如何取消以await WebClient.DownloadFileTaskAsync()开头的任务而不会引发异常？

最佳答案

唯一的例外是它应该如何工作。

如果您不希望该异常传播到事件处理程序之外，请捕获该异常。

关于c# - 在“await DownloadTaskAsync”上调用WebClient.CancelAsync时出现WebException，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/55870469/