Hi ! I am trying to integrate a twitter app into a wpf desktop application.I am using oauth-pin based authentication to access the tokens.I am able to get the access token and the access token secret, but im unable to post as it is showing a 403 exception.Any idea why? Ive been stuck for days 
Given below is the code for posting:
HttpWebRequest PostTwits(string oauth_consumer_key, string oauth_consumer_secret, string oauth_access_token, string oauth_token_secret, string postData)
{
postData = "trim_user=true&include_entities=true&status=" + postData;
string updateStatusURL = "https://api.twitter.com/1.1/statuses/update.json" ;
string outUrl;
string OAuthHeaderPOST = TwitterUtility.GetAuthorizationHeaderForPost_OR_QueryParameterForGET(new Uri(updateStatusURL), callbackUrl, httpMethod.POST.ToString(), oauth_consumer_key, oauth_consumer_secret, oauth_access_token, oauth_token_secret, out outUrl);
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(outUrl);
request.Method = httpMethod.POST.ToString();
request.Headers["Authorization"] = OAuthHeaderPOST;
byte[] array = Encoding.ASCII.GetBytes(postData);
request.GetRequestStream().Write(array, 0, array.Length);
return request;
}
public static string GetAuthorizationHeaderForPost_OR_QueryParameterForGET(Uri url, string callbackUrl, string httpMethod, string consumerKey, string consumerSecret, string token, string tokenSecret, out string normalizedUrl)
{
string normalizedParameters = "";
Dictionary<string, string> parameters = new Dictionary<string, string>();
parameters.Add("oauth_version", "1.0");
if (token != "")
parameters.Add("oauth_token", token);
parameters.Add("oauth_nonce", GenerateNonce()); //Random String
parameters.Add("oauth_timestamp", GenerateTimeStamp()); // Current Time Span
parameters.Add("oauth_consumer_key", consumerKey); //Customer Consumer Key
parameters.Add("oauth_signature_method", "HMAC-SHA1"); //Singnatur Encription Method
parameters.Add("oauth_callback", UrlEncode(callbackUrl)); //return url
Dictionary<string, string> drQuery = GetQueryParameters(url.Query);
foreach (string key in drQuery.Keys)
parameters.Add(key, drQuery[key]);
if (url.Query != "")
normalizedUrl = url.AbsoluteUri.Replace(url.Query, "");
else
normalizedUrl = url.AbsoluteUri;
List<string> li = parameters.Keys.ToList();
li.Sort();
StringBuilder sbOAuthHeader = new StringBuilder("OAuth ");
StringBuilder sbSignatureBase = new StringBuilder();
foreach (string k in li)
{
sbSignatureBase.AppendFormat("{0}={1}&", k, parameters[k]); // For Signature and Get Date (QueryString)
sbOAuthHeader.AppendFormat("{0}=\"{1}\", ", k, parameters[k]); // For Post Request (Post Data)
}
string signature = GenerateSignatureBySignatureBase(httpMethod, consumerSecret, tokenSecret, normalizedUrl, sbSignatureBase);
if (httpMethod == "POST")
{
string OAuthHeader = sbOAuthHeader.Append("oauth_signature=\"" + UrlEncode(signature) + "\"").ToString();
normalizedParameters = OAuthHeader;
}
else if (httpMethod == "GET")
{
normalizedParameters = sbSignatureBase.AppendFormat("{0}={1}", "oauth_signature", signature).ToString(); ;
}
return normalizedParameters;
}
private static string GenerateSignatureBySignatureBase(string httpMethod, string consumerSecret, string tokenSecret, string normalizedUrl, StringBuilder sbSignatureBase)
{
string normalizedRequestParameters = sbSignatureBase.ToString().TrimEnd('&');
StringBuilder signatureBase = new StringBuilder();
signatureBase.AppendFormat("{0}&", httpMethod.ToString());
signatureBase.AppendFormat("{0}&", UrlEncode(normalizedUrl));
signatureBase.AppendFormat("{0}", UrlEncode(normalizedRequestParameters));
HMACSHA1 hmacsha1 = new HMACSHA1();
hmacsha1.Key = Encoding.UTF8.GetBytes(string.Format("{0}&{1}", UrlEncode(consumerSecret), UrlEncode(tokenSecret)));
byte[] hashBytes = hmacsha1.ComputeHash(System.Text.Encoding.UTF8.GetBytes(signatureBase.ToString()));
return Convert.ToBase64String(hashBytes);
}
