title: OAuth authentication with VB.NET
body: <p>I'm trying to follow <a href="http://www.codeproject.com/Articles/247336/Twitter-OAuth-authentication-using-Net" rel="nofollow">this example</a> to access Twitter Stream API (userstream), so I need to do some modifications and this is my final code:</p>
  
  <pre><code>        'We need to define some details about the request. This includes a unique oauth_nonce parameter which must be generated per request, and a timestamp
          Dim oauth_version As String = "1.0"
          Dim oauth_signature_method As String = "HMAC-SHA1"
          Dim oauth_nonce As String = Convert.ToBase64String(New ASCIIEncoding().GetBytes(DateTime.Now.Ticks.ToString()))
          Dim TimeSpan = DateTime.UtcNow - New DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc)
          Dim oauth_timestamp As Integer = Convert.ToInt64(TimeSpan.TotalSeconds).ToString()
  
          'The next step is to generate an encrypted oAuth signature which Twitter will use to validate the request.
          'To do this, all of the request data is concatenated into a particular format as follows
          Dim baseFormat = "oauth_consumer_key={0}&amp;oauth_nonce={1}&amp;oauth_signature_method={2}" &amp; _
                           "&amp;oauth_timestamp={3}&amp;oauth_token={4}&amp;oauth_version={5}"
  
          Dim baseString As String = String.Format(baseFormat, _
                          oauth_consumer_key, _
                          oauth_nonce, _
                          oauth_signature_method, _
                          oauth_timestamp, _
                          oauth_token, _
                          oauth_version)
  
          'baseString = String.Concat("GET&amp;", Uri.EscapeDataString(stream_url), "&amp;", Uri.EscapeDataString(baseString))
          'baseString = String.Concat(Uri.EscapeDataString(stream_url), "&amp;", Uri.EscapeDataString(baseString))
          baseString = Uri.EscapeDataString(stream_url)
  
          'Using this base string, we then encrypt the data using a composite of the secret keys and the HMAC-SHA1 algorithm.
          Dim compositeKey As String = String.Concat(Uri.EscapeDataString(oauth_consumer_secret), "&amp;", Uri.EscapeDataString(oauth_token_secret))
          Dim oauth_signature As String
  
          Dim hasher As HMACSHA1 = New HMACSHA1(ASCIIEncoding.ASCII.GetBytes(compositeKey))
          Using hasher
              oauth_signature = Convert.ToBase64String(hasher.ComputeHash(ASCIIEncoding.ASCII.GetBytes(baseString)))
          End Using
  
          'The oAuth signature is then used to generate the Authentication header.
          'This requires concatenating the public keys and the token generated above into the following format
          Dim headerFormat As String = "OAuth oauth_nonce=""{0}"", oauth_signature_method=""{1}"", " &amp; _
                                         "oauth_timestamp=""{2}"", oauth_consumer_key=""{3}"", " &amp; _
                                         "oauth_token=""{4}"", oauth_signature=""{5}"", " &amp; _
                                         "oauth_version=""{6}"""
          Dim authHeader As String = 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))
  
          'We are now ready to send the request, which is the easy part.
          'Note, we must also disable the Expect: 100-Continue header using the ServicePointManager.
          'Without this code, .NET sends the header by default, which is not supported by Twitter
          Dim req As WebRequest
          Dim res As HttpWebResponse
          Dim streamReader As StreamReader
          Dim wait As Integer = 250
          Dim jsonRes As String = ""
          Dim encode As Encoding = System.Text.Encoding.GetEncoding("utf-8")
  
          ServicePointManager.Expect100Continue = False
          req = WebRequest.Create(stream_url)
          req.Headers.Add("Authorization", authHeader)
  
          res = DirectCast(req.GetResponse(), HttpWebResponse)
          streamReader = New StreamReader(res.GetResponseStream(), encode)
          While True
              jsonRes = streamReader.ReadLine()
  
              'Success
              wait = 250
          End While
  
          'Abort is needed or responseStream.Close() will hang
          req.Abort()
          streamReader.Close()
          streamReader = Nothing
          res.Close()
          res = Nothing
  </code></pre>
  
  <p>In this line: <em>res = DirectCast(req.GetResponse(), HttpWebResponse)</em> I get a <strong>401 - Unauthorized</strong>, I guess the problem might be in the line where I prepare the OAuth signature, the original used POST and I will need GET, so I changed it and tried these 3 alternatives:</p>
  
  <pre><code>        'baseString = String.Concat("GET&amp;", Uri.EscapeDataString(stream_url), "&amp;", Uri.EscapeDataString(baseString))
          'baseString = String.Concat(Uri.EscapeDataString(stream_url), "&amp;", Uri.EscapeDataString(baseString))
          baseString = Uri.EscapeDataString(stream_url)
  </code></pre>
  
  <p>Can you help me getting Twitter OAuth working in VB.NET?</p>
  
  <p>For the moment, Twitterizer is not an option as it only works with Visual Studio 2010, and TwitterVB2.dll only works with REST API, not streaming API, I don't know if there are other
  third party libraries but at this point I would prefer to solve in my own code (too many unmaintaned and incomplete libraries out there).</p>
  
  <p>Thank you</p>