如何为 HttpWebRequest 定义更激进的超时? [英] How to define a more aggressive timeout for HttpWebRequest?

问题描述

在可移植类库中，我使用以下方法将数据发布到特定的 Url.该方法效果很好.但是我想指定一个更激进的超时(默认为 100 秒).

Inside a Portable Class Library, I've the following method which post data to a specific Url. The method works great. However I'd like to specify a more aggressive timeout (the default is 100 seconds).

考虑到可移植类库中的 HttpWebRequest 类没有 Timeout 属性，如果调用时间超过几秒钟，我如何确保调用被放弃?

Considering that there's no Timeout property on the HttpWebRequest class from the Portable Class Library, how can I make sure that the call is abandoned if it takes longer than a few seconds?

public async Task<HttpResponse> PostAsync(Uri uri, string data)
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);
    request.Method = "POST";
    request.ContentType = "application/x-www-form-urlencoded";

    using (Stream requestStream = await request.GetRequestStreamAsync())
    {
        byte[] postBytes = Encoding.UTF8.GetBytes(data);
        requestStream.Write(postBytes, 0, postBytes.Length);
    }

    HttpWebResponse response = (HttpWebResponse)await request.GetResponseAsync();
    return new HttpResponse(response.StatusCode, await new StreamReader(response.GetResponseStream()).ReadToEndAsync());
}

推荐答案

如果超时，以下代码将返回 HttpWebResponse 或 null.

Below code either will return a HttpWebResponse or null if timed out.

HttpWebResponse response = await TaskWithTimeout(request.GetResponseAsync(), 100);
if(response != null)
{
  ....
}

<小时>

Task<HttpWebResponse> TaskWithTimeout(Task<WebResponse> task, int duration)
{
    return Task.Factory.StartNew(() =>
    {
        bool b = task.Wait(duration);
        if (b) return (HttpWebResponse)task.Result;
        return null;
    });
}

--编辑--

创建一个扩展方法会更好

Creating an extension method would be even better

public static class SOExtensions
{
    public static Task<T> WithTimeout<T>(this Task<T> task, int duration)
    {
        return Task.Factory.StartNew(() =>
        {
            bool b = task.Wait(duration);
            if (b) return task.Result;
            return default(T);
        });
    }
}

用法是:

var response = (HttpWebResponse)await request.GetResponseAsync().WithTimeout(1000);

--编辑 2--

另一种方式

public async static Task<T> WithTimeout<T>(this Task<T> task, int duration)
{
    var retTask = await Task.WhenAny(task, Task.Delay(duration))
                            .ConfigureAwait(false);

    if (retTask is Task<T>) return task.Result;
    return default(T);
}

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