从URL获取OAuth标头

Question

我有第三方网址，用于在标头中发送oAuth参数。当我使用下面的代码阅读它时，不会返回授权参数。我错过了什么？

string url = "http:  // xxx.com/events/abc-def";
            HttpClient httpClient = new HttpClient();

            WebRequest request = WebRequest.Create(url);
            request.Method = WebRequestMethods.Http.Get;
            string authHeader = request.Headers["Authorization"];