Extract 如何利用diggapi提取Digg数据

我正在尝试使用以下URL为用户提取Digg数据：

而web响应正在抛出一个错误。远程服务器返回了一个错误：403禁止

请让我知道

public static XmlTextReader CreateWebRequest(string url)
        {
            HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(url);
            webRequest.UserAgent = ".NET Framework digg Test Client";
            webRequest.Credentials = System.Net.CredentialCache.DefaultCredentials;
            webRequest.Accept = "text/xml";
            HttpWebResponse webResponse = (HttpWebResponse)webRequest.GetResponse();
            System.IO.Stream responseStream = webResponse.GetResponseStream();
            XmlTextReader reader = new XmlTextReader(responseStream);
            return reader;
        }