DotNetOpenAuth client for XING

XingClient.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Xml;
using System.Xml.Linq;
using DotNetOpenAuth.AspNet;
using DotNetOpenAuth.AspNet.Clients;
using DotNetOpenAuth.Messaging;
using DotNetOpenAuth.OAuth;
using DotNetOpenAuth.OAuth.ChannelElements;
using DotNetOpenAuth.OAuth.Messages;

namespace TechTalk.ExpertsPortal.Web.Infrastructure
{
    public class XingClient : OAuthClient
    {
        public static readonly ServiceProviderDescription TwitterServiceDescription = new ServiceProviderDescription
        {
            RequestTokenEndpoint =
                new MessageReceivingEndpoint(
                    "https://api.xing.com/v1/request_token",
                    HttpDeliveryMethods.GetRequest | HttpDeliveryMethods.AuthorizationHeaderRequest),
            UserAuthorizationEndpoint =
                new MessageReceivingEndpoint(
                    "https://api.xing.com/v1/authorize",
                    HttpDeliveryMethods.GetRequest | HttpDeliveryMethods.AuthorizationHeaderRequest),
            AccessTokenEndpoint =
                new MessageReceivingEndpoint(
                    "https://api.xing.com/v1/access_token",
                    HttpDeliveryMethods.GetRequest | HttpDeliveryMethods.AuthorizationHeaderRequest),
            TamperProtectionElements = new ITamperProtectionChannelBindingElement[] { new PlaintextSigningBindingElement()}
        };

        public XingClient(string consumerKey, string consumerSecret) :
            base("XING", TwitterServiceDescription, consumerKey, consumerSecret)
        {
            
        }

        public XingClient(string consumerKey, string consumerSecret, IOAuthTokenManager tokenManager) :
            base("XING", TwitterServiceDescription, new SimpleConsumerTokenManager(consumerKey, consumerSecret, tokenManager))
        {
        }

        protected override AuthenticationResult VerifyAuthenticationCore(AuthorizedTokenResponse response)
        {
            string accessToken = response.AccessToken;
            string userId = response.ExtraData["user_id"];
            string userName = userId;

            var profileRequestUrl = new Uri("https://api.xing.com/v1/users/me.xml?fields=permalink,active_email,display_name");
            var profileEndpoint = new MessageReceivingEndpoint(profileRequestUrl, HttpDeliveryMethods.GetRequest);
            HttpWebRequest request = this.WebWorker.PrepareAuthorizedRequest(profileEndpoint, accessToken);

            var extraData = new Dictionary<string, string>();
            extraData.Add("accesstoken", accessToken);
            try
            {
                using (WebResponse profileResponse = request.GetResponse())
                {
                    using (Stream responseStream = profileResponse.GetResponseStream())
                    {
                        XDocument document = LoadXDocumentFromStream(responseStream);
                        extraData.AddDataIfNotEmpty(document.Root.Element("user"), "permalink");
                        extraData.AddDataIfNotEmpty(document.Root.Element("user"), "active_email");
                        extraData.AddDataIfNotEmpty(document.Root.Element("user"), "display_name");
                    }
                }
            }
            catch (Exception)
            {
                // At this point, the authentication is already successful.
                // Here we are just trying to get additional data if we can.
                // If it fails, no problem.
            }

            if (extraData.ContainsKey("display_name"))
                userName = extraData["display_name"];

            return new AuthenticationResult(
                isSuccessful: true, provider: this.ProviderName, providerUserId: userId, userName: userName, extraData: extraData);
        }

        /// <summary>
        /// Helper method to load an XDocument from an input stream.
        /// </summary>
        /// <param name="stream">The input stream from which to load the document.</param>
        /// <returns>The XML document.</returns>
        internal static XDocument LoadXDocumentFromStream(Stream stream)
        {
            const int MaxChars = 0x10000; // 64k

            XmlReaderSettings settings = new XmlReaderSettings()
            {
                MaxCharactersInDocument = MaxChars,
            };
            return XDocument.Load(XmlReader.Create(stream, settings));
        }
    }
}

Nice work! :-) Got it working and XING returns the Token, but I'm wondering which kind of TokenManager I've got to pass to XING-Client:

XingClient xc = new XingClient("1bf...0", "7c...ed", ????);
AuthenticationResult rslt = xc.VerifyAuthentication(HttpContext);

Maybe you could provide a sample call to VerifyAuthentication?