Import contacts from Hotmail c# issue(There was an error deserializing the object of type OAuthToken. Encountered unexpected character '<'. )

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C#

ASP.NET

I am trying to import contacts from Hotmail. For that i am using following code

private const string wlCookie = "wl_auth";
private const string clientId = "...clientId...";
private const string callback = "http://localhost:8465/";
private const string clientSecret = "...secret key...";
private const string oauthUrl = "https://oauth.live.com/token";
public ActionResult Index(string code)
{
    if (code != null)
    {
        GetMsnContacts(Request.QueryString["code"].ToString());
    } 
   return View();
}
private void GetMsnContacts(string code)
{
    MsnImport msnImport = new MsnImport();
    List<string> emaillist = new List<string>();
    emaillist = msnImport.GetMsnContacts(code);
} 


msnImport.cs

public List<string> GetMsnContacts(string code)
    {

        try
        {
            HttpContext context = HttpContext.Current;
            string verifier = code;
            OAuthToken token;
            OAuthError error;

            if (!string.IsNullOrEmpty(verifier))
            {
                RequestAccessTokenByVerifier(verifier, out token, out error);
            }
        }
        catch (Exception ex) { }
        return emaillist;
    }
    private void RequestAccessTokenByVerifier(string verifier, out OAuthToken token, out OAuthError error)
    {
        string content = String.Format("client_id={0}&redirect_uri={1}&client_secret={2}&code={3}&grant_type=authorization_code",
        HttpUtility.UrlEncode(clientId),
        HttpUtility.UrlEncode(Callback),
        HttpUtility.UrlEncode(clientSecret),
        HttpUtility.UrlEncode(verifier));
        RequestAccessToken(content, out token, out error);
    }
    private void RequestAccessToken(string postContent, out OAuthToken token, out OAuthError error)
    {
        token = null;
        error = null;
        HttpWebRequest request = WebRequest.Create(oauthUrl) as HttpWebRequest;
        request.Method = "POST";
        try
        {
            using (StreamWriter writer = new StreamWriter(request.GetRequestStream()))
            {
                writer.Write(postContent);
            }
            HttpWebResponse response = request.GetResponse() as HttpWebResponse;
            if (response != null)
            {
                DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(OAuthToken));
                var objResponse = response.GetResponseStream();
                token = serializer.ReadObject(response.GetResponseStream()) as OAuthToken;
                if (token != null)
                {
                    RequestContacts(token.AccessToken);
                }
            }
        }
        catch (Exception ex)
        {

        }

    }

token = serializer.ReadObject(response.GetResponseStream()) as OAuthToken; this gives an error

e
{System.Runtime.Serialization.SerializationException: There was an error deserializing the object of type ContactsImport.Helper.OAuthToken. Encountered unexpected character '<'. ---> System.Xml.XmlException: Encountered unexpected character '<'.
   at System.Xml.XmlExceptionHelper.ThrowXmlException(XmlDictionaryReader reader, XmlException exception)
   at System.Runtime.Serialization.Json.XmlJsonReader.ReadAttributes()
   at System.Runtime.Serialization.Json.XmlJsonReader.ReadNonExistentElementName(StringHandleConstStringType elementName)
   at System.Runtime.Serialization.Json.XmlJsonReader.Read()
   at System.Xml.XmlBaseReader.IsStartElement()
   at System.Xml.XmlBaseReader.IsStartElement(XmlDictionaryString localName, XmlDictionaryString namespaceUri)
   at System.Runtime.Serialization.XmlReaderDelegator.IsStartElement(XmlDictionaryString localname, XmlDictionaryString ns)
   at System.Runtime.Serialization.XmlObjectSerializer.IsRootElement(XmlReaderDelegator reader, DataContract contract, XmlDictionaryString name, XmlDictionaryString ns)
   at System.Runtime.Serialization.Json.DataContractJsonSerializer.InternalIsStartObject(XmlReaderDelegator reader)
   at System.Runtime.Serialization.Json.DataContractJsonSerializer.InternalReadObject(XmlReaderDelegator xmlReader, Boolean verifyObjectName)
   at System.Runtime.Serialization.XmlObjectSerializer.InternalReadObject(XmlReaderDelegator reader, Boolean verifyObjectName, DataContractResolver dataContractResolver)
   at System.Runtime.Serialization.XmlObjectSerializer.ReadObjectHandleExceptions(XmlReaderDelegator reader, Boolean verifyObjectName, DataContractResolver dataContractResolver)
   --- End of inner exception stack trace ---
   at System.Runtime.Serialization.XmlObjectSerializer.ReadObjectHandleExceptions(XmlReaderDelegator reader, Boolean verifyObjectName, DataContractResolver dataContractResolver)
   at System.Runtime.Serialization.Json.DataContractJsonSerializer.ReadObject(XmlDictionaryReader reader)
   at System.Runtime.Serialization.Json.DataContractJsonSerializer.ReadObject(Stream stream)
   at ContactsImport.Helper.MsnImport.RequestAccessToken(String postContent, OAuthToken& token, OAuthError& error)

how we can solve this error?