Hi all

Am getting error message like
Please provide valid credentials. OAuth oauth_problem="unable_to_determine_oauth_type", realm="yahooapis.com"
i have attached sample coding for your reference please advise me where am going wrong..

Dim callback, normalizedrequestparameter, normalizedUrl As String
Dim consumerkey As String = "dj0yJmk9OE9qTTMzZmFkV2FEJmQ9WVdrOVIxbGpiMjVETmpRbWNHbzlNakEzTkRNNU5qZzJNZy0
tJnM9Y29uc3VtZXJzZWNyZXQmeD02Ng--"
Dim consumersecret As String = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
'oauth_tokendiv.InnerHtml = Request.QueryString("oauth_token")
'oauth_token_seceretdiv.InnerHtml = Request.QueryString("oauth_token_secret")
'yahoo_guiddiv.InnerHtml = Request.QueryString("yahoo_guid")
Session("token") = "A%3DhcUAob_ygjYfCDKu.10RgP3kW7t0L_BKKCQvgdEgVXuH5iI4WmhfrUS0Je8Ise.ouelGc8je.WvShw
BZAf2psd8JzAIFd.WtTpPBG8feKEWQyNojpKQHuN_ztmoQFM7NONmf9Fh9GmgFoB52zjYb8g38ZhfrQkx
NYkW8Fc5LdC9GAxZWwQFTaU0Z1G5hlcKh4R79c4HehSn7585lgQQya2DCc3jU7DgGVkVADiLab6FK6PwM
3fHdIApQLGLJcMVjyUI5tUcIfjEbiOZg0VIQMaJ18krQWltMhWleNTFWm9OU8e1BpaT3Shy6RbV8WE65u
pvzRqRFDbQ45O60S9BtMEGgP0.RAahEw1yFCvRHElWfXF.ojkFFTU8HvCn8FqSe0jrigqsBLYnW4eliMp
VAjsHO5Im7YJu3YHcN3C_.jkWn_g8C5VruY4nfU1JJNakG1x0NSQatuNxeKqu1GMlbA9KlAyzxKt0hUD9
vUUyeurFiYG6NsL_B69H0mXzzfmEJlpN.xn70TbNqVMOq.08TaF8sJUyWfPyLhCpMesws5VBOfind1Mdu
o.eXZSveZPYuLmPuBwvQNjTAMNzZ.MMP2IqPbXIJY_QBuTeOqHspgD_O0IF7WMtj9FQ9Uw2Fkmh01Ppdt
Xnkq1KgzM4Hh8eQQxuW9LMkN_zZLELA8ZNnh0M4DAWrTaacOYrjydEqEpZieHCI5mfH4nCc8t6U3gyuR1
pZmcW5Q30Wm9ZZAuYVtRHA6hAD1qMjFIaNRcf_io9rnONTeqvwiB0-"
Session("secret") = "ed8f9130bbec3f60e3278b9a2b39005f513dbaa0"
Session("guid") = "73773KQTGTQGYURA6XM5OIDXWA"

get_user()
End Sub
Public Function call_me() As String
Dim authorizationurl As String = ""
Dim oauth As New OAuthBase
Dim uri As New Uri("https://social.yahooapis.com/v1/user/" & Session("guid") & "/contacts")
'https://api.login.yahoo.com/oauth/v2/get_request_token
Dim nonce As String = oauth.GenerateNonce
Dim timestamp As String = oauth.GenerateTimeStamp
Dim sig As String = oauth.GenerateSignature(uri, consumerkey, consumersecret, Session("token"), Session("secret"), "GET", timestamp, nonce, OAuthBase.SignatureTypes.PLAINTEXT, normalizedUrl, normalizedrequestparameter)
'Dim sig As String = consumersecret & "%26" & Session("secret")
Dim requestedurl, dd As String
'sbrequesttoken = uri.ToString & "?oauth_consumer_key=" & consumerkey & "&oauth_signature_method=PLAINTEXT" & "&oauth_signature= " & sig & "&oauth_timestamp=" & timestamp & " &oauth_version= 1.0" & "&oauth_token=" & str1 & "&oauth_nonce=" & nonce & "&oauth_verifier=" & str & ""
dd = uri.ToString & "Authorization: OAuth" & "realm=yahooapis.com" & "oauth_consumer_key=" & consumerkey & "oauth_signature_method=PLAINTEXT" & "oauth_signature=" & sig & "oauth_timestamp=" & timestamp & "oauth_version= 1.0" & "oauth_token=" & Session("token") & "oauth_nonce=" & nonce
requestedurl = uri.ToString & "Authorization: OAuth" & "realm=yahooapis.com," & "oauth_consumer_key=" & consumerkey & ",oauth_nonce=" & nonce & ",oauth_signature_method=PLAINTEXT," & "oauth_timestamp=" & timestamp & ",oauth_token=" & Session("token") & ",oauth_version=1.0" & ",oauth_signature=" & sig
Dim requrl As String
reqUrl = "http://social.yahooapis.com/v1/user/" + Session("guid") + "/contacts?format=XML"
'reqUrl = reqUrl + "@realm=yahooapis.com"
requrl = requrl + ",oauth_consumer_key=" + consumerkey
requrl = requrl + ",oauth_nonce=" + nonce
requrl = requrl + ",oauth_signature_method=PLAINTEXT"
requrl = requrl + ",oauth_timestamp=" + timestamp
requrl = requrl + ",oauth_token=" + HttpUtility.UrlEncode(Session("token"))
requrl = requrl + ",oauth_version=1.0"
requrl = requrl + ",oauth_signature=" + sig
Return requrl
End Function
Public Sub get_user()
Dim url As String
url = call_me()
'Dim uri As String = HttpUtility.UrlEncode(url)
Dim req As HttpWebRequest = HttpWebRequest.Create(url)
'req.Credentials = CredentialCache.DefaultCredentials
req.Headers("Authorization") = "OAuth"
req.Headers("realm") = "yahooapis.com"
req.Method = "GET"
Dim res As HttpWebResponse = req.GetResponse
Dim sr As New StreamReader(res.GetResponseStream)
Dim str As String = sr.ReadToEnd
sr.Close()
show_user.InnerHtml = str
End Sub