400 bad request! I hate this error. Help pls!

dotnet

#1
twitterOAuthNonce = Convert.ToBase64String(New ASCIIEncoding().GetBytes(DateTime.Now.Ticks.ToString(CultureInfo.InvariantCulture)))
        Dim timeSpan = DateTime.UtcNow - New DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc)
        twitterOAuthTimestamp = Convert.ToInt64(timeSpan.TotalSeconds).ToString(CultureInfo.InvariantCulture)

        Dim baseString As String = "GET&" + Uri.EscapeDataString(twitterResourceURL)
        'Dim parameterString As String = "oauth_nonce=" + twitterOAuthNonce + "&oauth_signature_method=" + twitterOAuthSignatureMethod + "&oauth_timestamp=" + twitterOAuthTimestamp + "&oauth_consumer_key=" + twitterOAuthConsumerKey + "&oauth_version=1.0"
        Dim parameterString As String = "&oauth_consumer_key=" + twitterOAuthConsumerKey + "oauth_nonce=" + twitterOAuthNonce + "&oauth_signature_method=" + twitterOAuthSignatureMethod + "&oauth_timestamp=" + twitterOAuthTimestamp + "&oauth_version=1.0"
        baseString = baseString + "&" + Uri.EscapeDataString(parameterString)

        ' or Dim signingKey As String = Uri.EscapeDataString(twitterOAuthConsumerSecret) + "&" + Uri.EscapeDataString(twitterAccessTokenSecret)
        Dim signingKey As String = Uri.EscapeDataString(twitterOAuthConsumerSecret) + "&"

        Dim hasher As New HMACSHA1(New ASCIIEncoding().GetBytes(signingKey))
        twitterOAuthSignature = Convert.ToBase64String(hasher.ComputeHash(New ASCIIEncoding().GetBytes(baseString)))

        Dim Header As String = "OAuth " +
                               "oauth_nonce=""" + twitterOAuthNonce +
                               """oauth_callback=""" + twitterOAuthCallback +
                               """oauth_signature_method=""" + twitterOAuthSignatureMethod +
                               """oauth_timestamp=""" + twitterOAuthTimestamp +
                               """oauth_consumer_key=""" + twitterOAuthConsumerKey +
                               """oauth_signature=""" + twitterOAuthSignature +
                               """oauth_version=""" + twitterOAuthVersion


        Dim request As HttpWebRequest = DirectCast(WebRequest.Create(twitterResourceURL), HttpWebRequest)
        request.Headers.Add("Authorization", Header)
        request.ContentType = "application/x-www-form-urlencoded"
        request.Host = "api.twitter.com"
        request.Method = "POST"
        request.Proxy = Nothing

        Dim response As HttpWebResponse = request.GetResponse