Twitter look api 401 error - twitter

Question

Below code helped me to implement REST API calls with Twitter
var oauth_token = membership.Token; //"insert here...";
var oauth_token_secret = membership.TokenSecret; //"insert here...";
var oauth_consumer_key = consumerKey;
var oauth_consumer_secret = consumerSecret;
// oauth implementation details
var oauth_version = "1.0";
var oauth_signature_method = "HMAC-SHA1";
// unique request details
var oauth_nonce = Convert.ToBase64String(
new ASCIIEncoding().GetBytes(DateTime.Now.Ticks.ToString()));
var timeSpan = DateTime.UtcNow
- new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
var oauth_timestamp = Convert.ToInt64(timeSpan.TotalSeconds).ToString();
// create oauth signature
var baseFormat = "oauth_consumer_key={0}&oauth_nonce={1}&oauth_signature_method={2}" +
"&oauth_timestamp={3}&oauth_token={4}&oauth_version={5}";
var baseString = string.Format(baseFormat,
oauth_consumer_key,
oauth_nonce,
oauth_signature_method,
oauth_timestamp,
oauth_token,
oauth_version
);
baseString = string.Concat("GET&", Uri.EscapeDataString(resource_url), "&", Uri.EscapeDataString(baseString));
var compositeKey = string.Concat(Uri.EscapeDataString(oauth_consumer_secret),
"&", Uri.EscapeDataString(oauth_token_secret));
string oauth_signature;
using (HMACSHA1 hasher = new HMACSHA1(ASCIIEncoding.ASCII.GetBytes(compositeKey)))
{
oauth_signature = Convert.ToBase64String(
hasher.ComputeHash(ASCIIEncoding.ASCII.GetBytes(baseString)));
}
// create the request header
var headerFormat = "OAuth oauth_nonce=\"{0}\", oauth_signature_method=\"{1}\", " +
"oauth_timestamp=\"{2}\", oauth_consumer_key=\"{3}\", " +
"oauth_token=\"{4}\", oauth_signature=\"{5}\", " +
"oauth_version=\"{6}\"";
var authHeader = string.Format(headerFormat,
Uri.EscapeDataString(oauth_nonce),
Uri.EscapeDataString(oauth_signature_method),
Uri.EscapeDataString(oauth_timestamp),
Uri.EscapeDataString(oauth_consumer_key),
Uri.EscapeDataString(oauth_token),
Uri.EscapeDataString(oauth_signature),
Uri.EscapeDataString(oauth_version)
);
ServicePointManager.Expect100Continue = false;
// make the request
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(resource_url);
request.Headers.Add("Authorization", authHeader);
request.Method = "GET";
request.ContentType = "application/x-www-form-urlencoded";
var response = (HttpWebResponse)request.GetResponse();
var reader = new StreamReader(response.GetResponseStream());
var objText = reader.ReadToEnd();
return objText.ToString();
But the problem is that when I tried to implement https://api.twitter.com/1.1/statuses/lookup.json?id=20,432656548536401920 api it shows 401 error. The error comes only this api call only.