http - 如何解析在异步 http 发布期间发生的内部服务器错误？

Question

我在 Windows Phone 7 上做的通常是一个简单的 http post(下面的代码)。当我在帖子中查看 fiddler 时，我从服务器看到了这个结果

HTTP/1.1 500 Internal Server Error Cache-Control: private Content-Type: application/json; charset=utf-8 Server: Microsoft-IIS/7.5 jsonerror: true X-AspNet-Version: 2.0.50727 X-Server: www03 X-Site: prod Date: Tue, 16 Aug 2011 03:49:51 GMT Content-Length: 220

{"Message":"We’re sorry ... }

当我 try catch 异步帖子时，除了

之外我找不到任何东西

{System.Net.WebException: The remote server returned an error: NotFound. ---> System.Net.WebException: The remote server returned an error: NotFoun...

我的问题是:如何从此异常中获取实际消息(在 fiddler 中显示)？或者我怎样才能完全避免这个异常并取回 json，以便我可以解析它以获取实际的错误消息？

提前致谢

    public void Checkout(ResponseAndCookies responseAndCookies)
    {
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://localhost/checkout");
        request.ContentType = "application/json";
        request.CookieContainer = responseAndCookies.CookieContainer;
        request.Method = "POST";
        request.AllowAutoRedirect = false;
        request.Accept = "application/json";

        request.BeginGetRequestStream(new AsyncCallback(GetRequest), request);
    }

    private void GetRequest(IAsyncResult asyncResult)
    {
        var json = "{\"valid\":true}";
        byte[] byteArray = Encoding.UTF8.GetBytes(json);

        HttpWebRequest request = (HttpWebRequest) asyncResult.AsyncState;
        Stream newStream = request.EndGetRequestStream(asyncResult);
        newStream.Write(byteArray, 0, byteArray.Length);
        newStream.Close();

        request.BeginGetResponse(new AsyncCallback(GetResponse), request);
    }

    private void GetResponse(IAsyncResult asyncResult)
    {
            var response = ReadResponse(asyncResult); //if I try catch this I get the exception listed above :(
    }

    private ResponseAndCookies ReadResponse(IAsyncResult result)
    {
        Stream dataStream = null;
        HttpWebRequest request = (HttpWebRequest) result.AsyncState;
        HttpWebResponse response = request.EndGetResponse(result) as HttpWebResponse;
        dataStream = response.GetResponseStream();
        StreamReader reader = new StreamReader(dataStream);
        string responseFromServer = reader.ReadToEnd();
        reader.Close();
        dataStream.Close();
        response.Close();   

        var responseAndCookies = new ResponseAndCookies
                                     {CookieContainer = request.CookieContainer, Markup = responseFromServer};

        return responseAndCookies;
    }

Answer 1

HTTP 500 与“未找到”(即 HTTP 404)不同。所以你的异常(exception)实际上并不相关。无论如何，您显然需要阅读内容响应流。

您可以使用 WebException.Response 读取响应属性，在你的 catch 子句中。

话虽如此，我建议您研究一下类似 RestSharp 的框架.自己写那么多代码没意义。