在WP8.1中设置“超时时间10秒”为“HttpWebRequest”

Question

我需要为Wp8.1应用程序中的所有Http web请求设置10秒的超时。我没有在HttpWebRequest类中找到Timeout而不是ContinueTimeout属性。

快速搜索给了我们几个选择。使用CancellationToken是一个而另一个是使用Task。是否有人给我指点一下如何修改我当前的代码。

这是我如何创建一个请求

string uri = MyClass.HTTP_URI + "user/server-timestamps";
var request = (HttpWebRequest)WebRequest.Create(uri);
request.Method = MyClass.HTTP_GET;
request.Accept = "application/json";
request.Headers[HTTP_AUTHENTICATION_TOKEN] = "token"
request.Headers[API_KEY] = API_KEY_VALUE;

这是我发送请求的方式

     try
     {
          WebResponse responseObject = await Task<WebResponse>.Factory.FromAsync(request.BeginGetResponse, request.EndGetResponse, request);
          HttpWebResponse response = (HttpWebResponse)responseObject;
          statusCode = (int)response.StatusCode;
          if (statusCode == 200)
             {
                 var responseStream = responseObject.GetResponseStream();
                 var sr = new StreamReader(responseStream);
                 received = await sr.ReadToEndAsync();
                 //Do stuff
             }
     }

Answer 1

可以使用HttpClient类和CancellationTokenSource。修改一下。

try
{
     CancellationTokenSource cts = new CancellationTokenSource(2000);
     HttpClient client = new HttpClient();
     client.DefaultRequestHeaders.Accept.Add(new Windows.Web.Http.Headers.HttpMediaTypeWithQualityHeaderValue(""));
     HttpRequestMessage msg = new HttpRequestMessage(new HttpMethod("POST"), new Uri("Url"));
     HttpResponseMessage response = await client.SendRequestAsync(msg).AsTask(cts.Token);
}
catch(TaskCanceledException ex)
{
}

Answer 2

您可以创建一个接受CancellationToken的扩展方法，并像这样使用它:

var request = (HttpWebRequest)WebRequest.Create(uri);
// ...
try 
{
    using (var cts = new CancellationTokenSource(TimeSpan.FromSeconds(10)))
    {
        await request.GetResponseAsyncCancelable(cts.Token);
    }
}
catch (OperationCanceledException)
{
    // handle cancellation, if desired
}
// ...
public static class HttpWebRequestExt
{
    public static async Task<HttpWebResponse> GetResponseAsyncCancelable(
        this HttpWebRequest @this, 
        CancellationToken token)
    {
        using (token.Register(() => request.Abort(), useSynchronizationContext: false))
        {
            try
            {
                // BTW: any reason why not use request.GetResponseAsync,
                // rather than FromAsync? It's there in WP 8.1:
                // var response = await request.GetResponseAsync();
                var response = (HttpWebResponse)await Task<WebResponse>.Factory.FromAsync(request.BeginGetResponse, request.EndGetResponse, request);
                token.ThrowIfCancellationRequested();
                return response;
            }
            catch (WebException ex)
            {
                // WebException caused by cancellation?
                if (!token.IsCancellationRequested)
                    throw; // no, just re-throw
                // yes, wrap it with OperationCanceledException
                throw new OperationCanceledException(ex.Message, ex, token);
            }
        }
    }
}

顺便说一句，有什么原因你没有使用GetResponseAsync，这是在WP 8.1?