To send tweet using pure HTTP post with OAuth in C#

sendtweet.cs

//To send tweet using OAuth without any library
        private void SendTweet(string message)
        {
            try
            {
                string  _CK = "ConsumerKey"; //YOUR CONSUMER KEY
                string _CS = "ConsumerSecret"  //YOUR CONSUMER SECRET
                string _AT = "AccessToken" //Access Token
                string _ATS = "AccessTokenSecret " //Access Token Secret

                string authHeader = GenerateAuthorizationHeader(message);
                string postBody = "status=" + Uri.EscapeDataString(message);

                HttpWebRequest authRequest = (HttpWebRequest)WebRequest.Create(oAuthUrl);
                authRequest.Headers.Add("Authorization", authHeader);
                authRequest.Method = "POST";
                authRequest.UserAgent = "OAuth gem v0.4.4";
                authRequest.Host = "api.twitter.com";
                authRequest.ContentType = "application/x-www-form-urlencoded;charset=UTF-8";
                authRequest.ServicePoint.Expect100Continue = false;
                authRequest.AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate;
                ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
                using (Stream stream = authRequest.GetRequestStream())
                {
                    byte[] content = Encoding.UTF8.GetBytes(postBody);
                    stream.Write(content, 0, content.Length);
                }

                WebResponse authResponse = authRequest.GetResponse();
                authResponse.Close();

            }

            catch (System.Exception ea)
            {

                //handle exception
            }
        }
        private string GenerateAuthorizationHeader(string status)
        {
            string signatureMethod = "HMAC-SHA1";
            string version = "1.0";
            string nonce = GenerateNonce();
            double timestamp = ConvertToUnixTimestamp(DateTime.Now);
            string dst = string.Empty;

            dst = string.Empty;
            dst += "OAuth ";
            dst += string.Format("oauth_consumer_key=\"{0}\", ", Uri.EscapeDataString(_CK));
            dst += string.Format("oauth_nonce=\"{0}\", ", Uri.EscapeDataString(nonce));
            dst += string.Format("oauth_signature=\"{0}\", ", Uri.EscapeDataString(GenerateOauthSignature(status, nonce, timestamp.ToString())));
            dst += string.Format("oauth_signature_method=\"{0}\", ", Uri.EscapeDataString(signatureMethod));
            dst += string.Format("oauth_timestamp=\"{0}\", ", timestamp);
            dst += string.Format("oauth_token=\"{0}\", ", Uri.EscapeDataString(_AT));
            dst += string.Format("oauth_version=\"{0}\"", Uri.EscapeDataString(version));
            return dst;
        }
        private string GenerateOauthSignature(string status, string nonce, string timestamp)
        {
            string signatureMethod = "HMAC-SHA1";
            string version = "1.0";
            string result = string.Empty;
            string dst = string.Empty;

            dst += string.Format("oauth_consumer_key={0}&", Uri.EscapeDataString(_CK));
            dst += string.Format("oauth_nonce={0}&", Uri.EscapeDataString(nonce));
            dst += string.Format("oauth_signature_method={0}&", Uri.EscapeDataString(signatureMethod));
            dst += string.Format("oauth_timestamp={0}&", timestamp);
            dst += string.Format("oauth_token={0}&", Uri.EscapeDataString(_AT));
            dst += string.Format("oauth_version={0}&", Uri.EscapeDataString(version));
            dst += string.Format("status={0}", Uri.EscapeDataString(status));

            string signingKey = string.Empty;
            signingKey = string.Format("{0}&{1}", Uri.EscapeDataString(_CS), Uri.EscapeDataString(_ATS));

            result += "POST&";
            result += Uri.EscapeDataString(oAuthUrl);
            result += "&";
            result += Uri.EscapeDataString(dst);

            HMACSHA1 hmac = new HMACSHA1();
            hmac.Key = Encoding.UTF8.GetBytes(signingKey);

            byte[] databuff = System.Text.Encoding.UTF8.GetBytes(result);
            byte[] hashbytes = hmac.ComputeHash(databuff);

            return Convert.ToBase64String(hashbytes);
        }
        private string GenerateNonce()
        {
            string nonce = string.Empty;
            var rand = new Random();
            int next = 0;
            for (var i = 0; i < 32; i++)
            {
                next = rand.Next(65, 90);
                char c = Convert.ToChar(next);
                nonce += c;
            }

            return nonce;
        }
        public static double ConvertToUnixTimestamp(DateTime date)
        {
            DateTime origin = new DateTime(1970, 1, 1, 0, 0, 0, 0);
            TimeSpan diff = date.ToUniversalTime() - origin;
            return Math.Floor(diff.TotalSeconds);
        }