Twitter API v1.1 OAuth で認証し、HttpWebRequest を使用してユーザーのタイムラインを取得するにはどうすればよいですか?

<code class="language-csharp">//  Assume these variables are pre-populated:
//  oAuthConsumerKey: Your OAuth consumer key
//  oAuthConsumerSecret: Your OAuth consumer secret
//  screenname: The target Twitter username

// Authentication
string authHeaderFormat = "Basic {0}";
string authHeader = string.Format(authHeaderFormat,
    Convert.ToBase64String(Encoding.UTF8.GetBytes(Uri.EscapeDataString(oAuthConsumerKey) + ":" +
    Uri.EscapeDataString(oAuthConsumerSecret))));
string postBody = "grant_type=client_credentials";
HttpWebRequest authRequest = (HttpWebRequest)WebRequest.Create("https://api.twitter.com/oauth2/token");
authRequest.Headers.Add("Authorization", authHeader);
authRequest.Method = "POST";
authRequest.ContentType = "application/x-www-form-urlencoded;charset=UTF-8";
authRequest.AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate;

using (Stream stream = authRequest.GetRequestStream())
{
    byte[] content = ASCIIEncoding.ASCII.GetBytes(postBody);
    stream.Write(content, 0, content.Length);
}

authRequest.Headers.Add("Accept-Encoding", "gzip");
HttpWebResponse authResponse = (HttpWebResponse)authRequest.GetResponse();

// Deserialize authentication response
TwitterAuthResponse authResponseObject;
using (authResponse)
{
    using (StreamReader reader = new StreamReader(authResponse.GetResponseStream()))
    {
        string json = reader.ReadToEnd();
        authResponseObject = JsonConvert.DeserializeObject<TwitterAuthResponse>(json);
    }
}

// Timeline Request
string timelineFormat = "https://api.twitter.com/1.1/statuses/user_timeline.json?screen_name={0}&include_rts=1&exclude_replies=1&count=5";
string timelineUrl = string.Format(timelineFormat, screenname);
HttpWebRequest timelineRequest = (HttpWebRequest)WebRequest.Create(timelineUrl);
string timelineHeaderFormat = "{0} {1}";
timelineRequest.Headers.Add("Authorization", string.Format(timelineHeaderFormat, authResponseObject.token_type, authResponseObject.access_token));
timelineRequest.Method = "GET";
HttpWebResponse timelineResponse = (HttpWebResponse)timelineRequest.GetResponse();


// Parse timeline response
string timelineJson;
using (timelineResponse)
{
    using (StreamReader reader = new StreamReader(timelineResponse.GetResponseStream()))
    {
        timelineJson = reader.ReadToEnd();
    }
}

// Process the timelineJson data.</code>