How to get the id of a Facebook user with the SDK for .NET?

Question

I am using Facebook SDK for .NET 7.0.6

With this code I can get name, first name, last name and other attributes, but not the id of the user.

    var _fb = new FacebookClient(Session["FbuserToken"].ToString());
    dynamic resultMe = _fb.Get("me?fields=id");
    return resultMe.id;

How can I get it?

Answer 1

IDs are "App Scoped", a user will get a different (but unique) ID per App. In the API Explorer, you most likely did not select YOUR App, but only the official API Explorer App - which results in a different ID, of course.

In other words: You DO get an ID, and it is the correct one to identify returning users.

Answer 2

HomeController.cs

    using Facebook;
using Newtonsoft.Json.Linq;
using System;
using System.Collections.Generic;
using System.Dynamic;
using System.Linq;
using System.Net;
using System.Web;
using System.Web.Mvc;

namespace FaceTest.Controllers
{
    public class HomeController : Controller
    {
        public ActionResult Index()
        {
            ViewBag.UrlFb = GetFacebookLoginUrl();
            return View();
        }

        public ActionResult About()
        {
            //ViewBag.Message = "Your application description page.";
            ViewBag.Name = !String.IsNullOrEmpty(GetProfileName()) ? GetProfileName() : "Inicia Sesión";
            ViewBag.Id = !String.IsNullOrEmpty(GetProfileId()) ? GetProfileId() : "Inicia Sesión";
            return View();
        }

        public ActionResult Contact()
        {
            ViewBag.Message = "Your contact page.";

            return View();
        }

        public string GetFacebookLoginUrl()
        {
            dynamic parameters = new ExpandoObject();
            parameters.client_id = "1766341193627031";
            parameters.redirect_uri = "http://localhost:51518/Home/RetornoFb/";
            parameters.response_type = "code";
            parameters.display = "page";

            var extendedPermissions = "publish_actions";
            parameters.scope = extendedPermissions;

            var _fb = new FacebookClient();
            var url = _fb.GetLoginUrl(parameters);

            return url.ToString();
        }

        public ActionResult RetornoFb()
        {
            var _fb = new FacebookClient();
            FacebookOAuthResult oauthResult;

            if(!_fb.TryParseOAuthCallbackUrl(Request.Url, out oauthResult))
            {
                // Error
            }

            if (oauthResult.IsSuccess)
            {
                //Pega o Access Token "permanente"
                dynamic parameters = new ExpandoObject();
                parameters.client_id = "1766341193627031";
                parameters.redirect_uri = "http://localhost:51518/Home/RetornoFb/";
                parameters.client_secret = "52cee8ef9437e4981302c24a66e13d55";
                parameters.code = oauthResult.Code;

                dynamic result = _fb.Get("/oauth/access_token", parameters);

                var accessToken = result.access_token;

                //TODO: Guardar no banco
                Session.Add("FbUserToken", accessToken);
            }
            else
            {
                // tratar
            }

            return RedirectToAction("Index");
        }

        public ActionResult DetalhesDoUsuario()
        {
            if (Session["FbuserToken"] != null)
            {
                var _fb = new FacebookClient(Session["FbuserToken"].ToString());

                //detalhes do usuario
                var request = _fb.Get("me");
                var a = request;
            }

            return RedirectToAction("Index");
        }
/* ------------------------------------------------------------------------------------------------------------------------------------------------ */
        /* public string GetName(string externalToken)
         {
             FacebookClient client = new FacebookClient(externalToken);
             dynamic resultMe = client.Get("me?fields=id,name");

             return resultMe.Name;
         }*/

        public string GetProfileName()
        {
            if (Session["FbuserToken"] != null)
            {
                try
                {
                    var _fb = new FacebookClient(Session["FbuserToken"].ToString());
                    dynamic resultMe = _fb.Get("me?fields=first_name");
                    return resultMe.first_name;
                }
                catch (FacebookOAuthException)
                {
                    return null;
                }
            }

            return null;
        }

        public string GetProfileId()
        {

            if (Session["FbuserToken"] != null)
            {
                try
                {
                    var _fb = new FacebookClient(Session["FbuserToken"].ToString());
                    dynamic resultMe = _fb.Get("me?fields=id");
                    return resultMe.id;
                }
                catch (FacebookOAuthException)
                {
                    return null;
                }
            }

            return null;
        }
        /* ------------------------------------------------------------------------------------------------------------------------------------------------ */
        /*public byte[] GetPhoto(string userId)
            {
                try
                {
                    string url = "https://graph.facebook.com/" + userId + 
                                 "?fields=picture.width(720).height(720)";

                    WebClient webClient = new WebClient();
                    string response = webClient.DownloadString(url);

                    dynamic json = JObject.Parse(response);

                    string urlPicture = json.picture.data.url;

                    return webClient.DownloadData(urlPicture);
                }
                catch (Exception)
                {
                    return null;
                }
            }*/
        public byte[] GetPhoto()
        {
            try
            {
                string url = "https://graph.facebook.com/" + GetProfileId() +"?fields=picture.width(480).height(480)";

                WebClient webClient = new WebClient();
                string response = webClient.DownloadString(url);

                dynamic json = JObject.Parse(response);

                string urlPicture = json.picture.data.url;

                return webClient.DownloadData(urlPicture);
            }
            catch (Exception)
            {
                return null;
            }
        }
/* ------------------------------------------------------------------------------------------------------------------------------------------------ */
/*  */
/* ------------------------------------------------------------------------------------------------------------------------------------------------ */

    /*
     protected IEnumerable<string> GetFriendIds(string externalToken)
        {
            FacebookClient client = new FacebookClient(externalToken);
            dynamic result = client.Get("me/friends");

            foreach (dynamic friend in result.data)
            {
                yield return friend.id;
            }
        }
    */
/* ------------------------------------------------------------------------------------------------------------------------------------------------ */
        public ActionResult ListarAmigos()
        {
            if (Session["FbuserToken"] != null)
            {
                var _fb = new FacebookClient(Session["FbuserToken"].ToString());

                //listar os amigos
                var request = _fb.Get("me/friends");
                var a = request;
            }

            return RedirectToAction("Index");

        }
/* ------------------------------------------------------------------------------------------------------------------------------------------------ */
    /*
    public void Share(string userId, string externalToken, Yipi yipi)
        {
            dynamic messagePost = new ExpandoObject();
            messagePost.link = GetYipiUrl(yipi);
            messagePost.message = string.Format(TextMessage, yipi.Message);

            FacebookClient client = new FacebookClient(externalToken);
            client.Post(userId + "/feed", messagePost);
        } 
    */
/* ------------------------------------------------------------------------------------------------------------------------------------------------ */
        public ActionResult PublicarMensagem()
        {
            if (Session["FbuserToken"] != null)
            {
                var _fb = new FacebookClient(Session["FbuserToken"].ToString());

                //Postar uma mensagem na timeline
                dynamic messagePost = new ExpandoObject();
                messagePost.picture = "http://www.rodolfofadino.com.br/wp-content/uploads/2013/12/image_thumb10.png";
                messagePost.link = "http://www.rodolfofadino.com.br/2013/12/test-mode-values-para-o-microsoft-advertising-sdk-windows-8/";
                messagePost.name = "Post name...";
                messagePost.caption = " Post Caption";
                messagePost.description = "post description";
                messagePost.message = "Mensagem de testes da aplicação";

                try
                {
                    var postId = _fb.Post("me/feed", messagePost);
                }
                catch (FacebookOAuthException ex)
                {
                    //handle oauth exception
                }
                catch (FacebookApiException ex)
                {
                    //handle facebook exception
                }
            }

            return RedirectToAction("Index");
        }

        public ActionResult PublicarFoto()
        {
            if (Session["FbuserToken"] != null)
            {
                var _fb = new FacebookClient(Session["FbuserToken"].ToString());
                //upload de imagem
                FacebookMediaObject media = new FacebookMediaObject
                {
                    FileName = "Nome da foto",
                    ContentType = "image/jpeg"
                };

                byte[] img = System.IO.File.ReadAllBytes(Server.MapPath("~/Content/rodolfo.jpg"));
                media.SetValue(img);

                dynamic parameters = new ExpandoObject();

                parameters.source = media;
                parameters.message = "Descricao";

                try
                {
                    dynamic result = _fb.Post("/me/photos", parameters);

                }
                catch (Exception ex)
                {
                }
            }
            return RedirectToAction("Index");
        }
    }
}

index.cshtml

@{
    ViewBag.Title = "Home Page";
}

<div class="jumbotron">
    <h1>ASP.NET + Facebook</h1>
    <p><a href="@ViewBag.UrlFb" class="btn btn-primary btn-large">Login Facebook</a></p>
</div>

About.cshtml

@{
  ViewBag.Title = "About";
}
<h2>@ViewBag.Title.</h2>
<h3>@ViewBag.Name</h3>

<p>@ViewBag.Id</p>