仅在第一个HTTP请求中获得空响应Windows Phone 8

Question

每当我在Windows Phone 8中启动应用程序并发送http GET请求时，我都会得到空响应。 这只是第一个请求，其他请求对相同url的响应也不为空。

这是代码：

string res = "";

private void ReadUrlAsync(string url)
    {
        var request = HttpWebRequest.Create(new Uri(url)) as HttpWebRequest;
       // request.Accept = "application/json;odata=verbose";
        request.BeginGetResponse(ResponseCallback, request);
    }

    private void ResponseCallback(IAsyncResult asyncResult)
    {
        HttpWebRequest request = (HttpWebRequest)asyncResult.AsyncState;
        HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(asyncResult);
        string data;
        using (Stream responseStream = response.GetResponseStream())
        {

            using (var reader = new System.IO.StreamReader(responseStream))
            {
                data = reader.ReadToEnd();
            }
        }
        res = data;
    }

Answer 1

我使用了一些不同的代码并找到了解决方案：

        HttpClient cl = new HttpClient();
       return await cl.GetStringAsync(new Uri(url));