C# implement oauth 1.0 by using HMAC-SHA1 (without token)

Question

I have tried to implement the Oauth 1.0 by using HMAC-SHA1 (without token details). While debug it, It's always return the following exception "The remote server returned an error: (401) Unauthorized". But the same credential works fine in Postman.

I have the Token secret

var key = EscapeUriDataStringRfc3986(consumerSecret) + "&";" 

as well while form the key details.

try
{
    var httpWebRequest = (HttpWebRequest)WebRequest.Create(url);
    httpWebRequest.Method = "GET";

    var timeStamp = ((int)(DateTime.UtcNow - new DateTime(1970, 1, 1)).TotalSeconds).ToString();
    var nonce = Convert.ToBase64String(Encoding.UTF8.GetBytes(timeStamp));

    var signatureBaseString = Escape(httpWebRequest.Method.ToUpper()) + "&";
    signatureBaseString += EscapeUriDataStringRfc3986(url.ToLower()) + "&";
    signatureBaseString += EscapeUriDataStringRfc3986(
        "oauth_consumer_key=" + EscapeUriDataStringRfc3986(consumerKey) + "&" +
        "oauth_nonce=" + EscapeUriDataStringRfc3986(nonce) + "&" +
        "oauth_signature_method=" + EscapeUriDataStringRfc3986("HMAC-SHA1") + "&" +
        "oauth_timestamp=" + EscapeUriDataStringRfc3986(timeStamp) + "&" +
        "oauth_version=" + EscapeUriDataStringRfc3986("1.0"));
    //MessageBox.Show(@"signatureBaseString: " + signatureBaseString);

    var key = EscapeUriDataStringRfc3986(consumerSecret) + "&";
    MessageBox.Show(@"key: " + key);
    var signatureEncoding = new ASCIIEncoding();
    var keyBytes = signatureEncoding.GetBytes(key);
    var signatureBaseBytes = signatureEncoding.GetBytes(signatureBaseString);
    string signatureString;
    using (var hmacsha1 = new HMACSHA1(keyBytes))
    {
        var hashBytes = hmacsha1.ComputeHash(signatureBaseBytes);
        signatureString = Convert.ToBase64String(hashBytes);
    }
    signatureString = EscapeUriDataStringRfc3986(signatureString);
    MessageBox.Show(@"signatureString: " + signatureString);

    var header =
            "oauth_consumer_key=" + SimpleQuote(consumerKey) + "," +
            "oauth_nonce=" + SimpleQuote(nonce) + "," +
            "oauth_signature_method=" + SimpleQuote("HMAC-SHA1") + "," +
            "oauth_timestamp=" + SimpleQuote(timeStamp) + "," +
            "oauth_version=" + SimpleQuote("1.0") + "," +
            "oauth_signature= " + SimpleQuote(signatureString);

    MessageBox.Show(@"header: " + header);
    httpWebRequest.Headers.Add(HttpRequestHeader.Authorization, header);

    var response = httpWebRequest.GetResponse();
    var characterSet = ((HttpWebResponse)response).CharacterSet;
    var responseEncoding = characterSet == ""
        ? Encoding.UTF8
        : Encoding.GetEncoding(characterSet ?? "utf-8");
    var responsestream = response.GetResponseStream();
    if (responsestream == null)
    {
        //throw new ArgumentNullException(nameof(characterSet));
    }
    using (responsestream)
    {
        var reader = new StreamReader(responsestream, responseEncoding);
        var result = reader.ReadToEnd();
        Console.WriteLine(@"result: " + result);
    }
}
catch (Exception ex)
{
    MessageBox.Show("Error:"+ex.Message.ToString());
}