public partial class MainPage : UserControl
    {
        public string accesstoken;

        public MainPage()
        {
            InitializeComponent();
            LoginToFacebook();
        }

        void LoginToFacebook()
        {
            string appId = "app_id";
            string[] extendedPermissions = new[] { "publish_stream", "offline_access" };

            var oauth = new FacebookOAuthClient() { AppId = appId };
            var parameters = new Dictionary<string, object>
                {
                    { "response_type", "code" },
                    { "display", "popup" }
                };

            if (extendedPermissions != null && extendedPermissions.Length > 0)
            {
                var scope = new StringBuilder();
                scope.Append(string.Join(",", extendedPermissions));
                parameters["scope"] = scope.ToString();
            }

            var loginUrl = oauth.GetLoginUrl(parameters);
        }

        void oauth_GetApplicationAccessTokenCompleted(object sender, FacebookApiEventArgs e)
        {
        }
    }