HttpWebRequest.GetResponse（）上的空响应？

Question

我正在使用http://dictionary.reference.com/browse/:word并检查返回的响应的状态，以评估“单词”定义是否存在。它适用于正确的单词（200状态代码）。但对于那些拼写不正确的人（404状态代码），我无法从HttpWebRequest.GetResponse（）中捕获状态代码，因为它返回null？

问题是我正在使用PostMan进行检查，我确实收到了以下网址的状态码404：

http://dictionary.reference.com/browse/sdfsdsdc

这是我的实施：

string baseURL = "http://dictionary.reference.com/browse";
bool result = false;
try
{                
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(baseURL + "/" + word);
    request.Method = "GET";
    //request.Timeout = 2000;
    request.KeepAlive = false;
    request.ContentType = "text/html; charset=UTF-8";
    Console.WriteLine(request.RequestUri);
    HttpWebResponse response = (HttpWebResponse)request.GetResponse();

    HttpStatusCode statusCode = response.StatusCode;
    int statusCodeNumber = (int)statusCode;

    Console.WriteLine("Status Code: " + statusCode + " - status number: " + statusCodeNumber);
    try
    {
        if (statusCodeNumber == 200) result = true;
        else if (statusCodeNumber == 404) { result = false; }
        else { throw new UnknownStatusCodeException(); }
    }
    catch (UnknownStatusCodeException e) {}
    response.Close();                
    }
    catch (WebException e) {
    }
}

这是我抓到的WebException

full-size-pic

有人可以给我一些指示吗？感谢