C#超时后中止异步HttpWebRequest

Question

我在这里找到了https://stackoverflow.com/a/19215782/4332018将 CancellationToken 与 async HttpWebRequest 结合使用的一个很好的解决方案:

public static class Extensions
{
    public static async Task<HttpWebResponse> GetResponseAsync(this HttpWebRequest request, CancellationToken ct)
    {
        using (ct.Register(() => request.Abort(), useSynchronizationContext: false))
        {
            try
            {
                var response = await request.GetResponseAsync();
                return (HttpWebResponse)response;
            }
            catch (WebException ex)
            {
                // WebException is thrown when request.Abort() is called,
                // but there may be many other reasons,
                // propagate the WebException to the caller correctly
                if (ct.IsCancellationRequested)
                {
                    // the WebException will be available as Exception.InnerException
                    throw new OperationCanceledException(ex.Message, ex, ct);
                }

                // cancellation hasn't been requested, rethrow the original WebException
                throw;
            }
        }
    }
}

但我不明白如果执行时间超过预设时间，我该如何中止 request。

我知道 CancellationTokenSource() 和 CancelAfter(Int32)，但不明白如何修改上面的示例以使用 CancellationTokenSource , 因为它没有 Register 方法。

我如何制作一个async HttpWebRequest 并且可以在预设时间后取消？

Answer 1

创建 token 源时，设置取消。然后传入token。它应该超时。

CancellationTokenSource cts = new CancellationTokenSource();
                cts.CancelAfter(1000);

                var ct = cts.Token;

                var httpWebRequest = (HttpWebRequest)WebRequest.Create("http://www.zzz.com/here");
                var test = Extensions.GetResponseAsync(httpWebRequest, ct);