public App()
        {
            OAuthSettings = new OAuthSettings(
                                    clientId: FacebookClientId,
                                    scope: "user_birthday,user_friends,user_about_me,user_status,user_posts,email,public_profile",
                                    authorizeUrl: "https://m.facebook.com/dialog/oauth/",
                                    redirectUrl: "http://www.facebook.com/connect/login_success.html");
            AppUsers = InitializeUsers();

            HomePage = new HomePage();
            NavPage = new NavigationPage(HomePage);

            // The root page of your application
            MainPage = NavPage;
        }
        public App()
        {
            OAuthSettings = new OAuthSettings(
                clientId: FacebookClientId,
                scope: "user_birthday,user_friends,user_about_me,user_status,user_posts,email,public_profile",
                authorizeUrl: "https://m.facebook.com/dialog/oauth/",
                redirectUrl: "http://www.facebook.com/connect/login_success.html");
            AppUsers = InitializeUsers();

            HomePage = new HomePage();
            NavPage  = new NavigationPage(HomePage);

            // The root page of your application
            MainPage = NavPage;
        }