使用c＃从Hotmail导入联系人

Question

我正在尝试从Hotmail导入联系人。为此，我使用以下代码

 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;这给出了一个错误。

{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)

我们如何解决这个错误？