how to post to facebook page wall from .NET

Question

I've created Facebook page. I have no application secret and no access token.

I want to post to this page from my .NET desktop application. How can I do it? Can anyone help please, where can I get access token for this?

Should I create a new Facebook Application? If yes, how can I grant permissions to this application to post on page's wall?

UPD1: I have no website. I need to post company's news from .NET desktop application to company's Facebook page. All I have is Login/Password for Facebook Page Account.

UPD2: I've created Facebook Application. With AppID/SecretKey. I can get access token. But... How can I grant permissions to post to page's wall?

(OAuthException) (#200) The user hasn't authorized the application to perform this action

Answer 1

You can use https://www.nuget.org/packages/Microsoft.Owin.Security.Facebook/ to obtain users login and permission and https://www.nuget.org/packages/Facebook.Client/ to post to feeds.

Below example is for ASP.NET MVC 5:

public void ConfigureAuth(IAppBuilder app)
        {
            app.UseExternalSignInCookie(DefaultAuthenticationTypes.ExternalCookie);

            // Facebook 
            var facebookOptions = new FacebookAuthenticationOptions
            {
                AppId = "{get_it_from_dev_console}",
                AppSecret = "{get_it_from_dev_console}",
                BackchannelHttpHandler = new FacebookBackChannelHandler(),
                UserInformationEndpoint = "https://graph.facebook.com/v2.4/me?fields=id,name,email,first_name,last_name,location",
                Provider = new FacebookAuthenticationProvider
                {
                    OnAuthenticated = context =>
                    {
                        context.Identity.AddClaim(new Claim("FacebookAccessToken", context.AccessToken)); // user acces token needed for posting on the wall 
                        return Task.FromResult(true);
                    }
                }
            };
            facebookOptions.Scope.Add("email");
            facebookOptions.Scope.Add("publish_actions"); // permission needed for posting on the wall 
            facebookOptions.Scope.Add("publish_pages"); // permission needed for posting on the page
            app.UseFacebookAuthentication(facebookOptions);

            AntiForgeryConfig.UniqueClaimTypeIdentifier = ClaimTypes.NameIdentifier;
        }
    }

On the callback you get user access token:

public ActionResult callback()
{
    // Here we skip all the error handling and null checking
    var auth = HttpContext.GetOwinContext().Authentication;
    var loginInfo = auth.GetExternalLoginInfo();
    var identityInfo = auth.GetExternalIdentity(DefaultAuthenticationTypes.ExternalCookie);

    var email = loginInfo.Email // [e-mail]
    var name = loginInfo.ExternalIdentity.Name  // Klaatu Verata Necto
    var provider = loginInfo.Login.LoginProvider // Facebook | Google

    var fb_access_token = loginInfo.identityInfo.FindFirstValue("FacebookAccessToken");
    // Save this token to database, for the purpose of this example we will save it to Session.
    Session['fb_access_token'] = fb_access_token;
    // ...                   
}

Which then you can use to post to user's feed or page

public class postcontroller : basecontroller
{                      
        public ActionResult wall()
        {
            var client = new FacebookClient( Session['fb_access_token'] as string);
            var args = new Dictionary<string, object>();
            args["message"] = "Klaatu Verata N......(caugh, caugh)";

            try
            {
                client.Post("/me/feed", args); // post to users wall (feed)
                client.Post("/{page-id}/feed", args); // post to page feed
            }
            catch (Exception ex)
            {
                // Log if anything goes wrong 
            }

        }
}

I posted full example over here: https://klaatuveratanecto.com/facebook-wall-feed-posting-asp-net-mvc/

Answer 2

You will get information on how to create a facebook app or link your website to facebook on https://developers.facebook.com/?ref=pf.

You will be able to download facebook sdk at http://facebooksdk.codeplex.com/. There are some good example given in the document section of the site.

Answer 3

public void PostImageOnPage()
{
string filename=string.Empty;
if(ModelState.IsValid)
{
//-------- save image in image/
if (System.Web.HttpContext.Current.Request.Files.Count > 0)
{
var file = System.Web.HttpContext.Current.Request.Files[0];
// fetching image                    
filename = Path.GetFileName(file.FileName);
filename = DateTime.Now.ToString("yyyyMMdd") + "_" + filename;
file.SaveAs(Server.MapPath("~/images/Advertisement/") + filename);
}
}
string Picture_Path = Server.MapPath("~/Images/" + "image3.jpg");
string message = "my message";
try
{
string PageAccessToken = "EAACEdEose0cBAAoWM3X";

// ————————create the FacebookClient object
FacebookClient facebookClient = new FacebookClient(PageAccessToken);

// ————————set the parameters
dynamic parameters = new ExpandoObject();
parameters.message = message;
parameters.Subject = "";
parameters.source = new FacebookMediaObject
{
ContentType = "image/jpeg",
FileName = Path.GetFileName(Picture_Path)
}.SetValue(System.IO.File.ReadAllBytes(Picture_Path));
// facebookClient.Post("/" + PageID + "/photos", parameters);// working for notification on user page
facebookClient.Post("me/photos", parameters);// woring using bingoapp access token not page in(image album) Post the image/picture to User wall   
}
catch (Exception ex)
{

}
}

Answer 4

I have created a video tutorial showing how to do this at this location:

http://www.markhagan.me/Samples/Grant-Access-And-Post-As-Facebook-User-ASPNet

You will notice that, in my example, I am asking for both "publish_stream" and "manage_pages". This let's you also post on pages of which that users is an admin. Here is the full code:

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

using Facebook;

namespace FBO
{
    public partial class facebooksync : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            CheckAuthorization();
        }

        private void CheckAuthorization()
        {
            string app_id = "374961455917802";
            string app_secret = "9153b340ee604f7917fd57c7ab08b3fa";
            string scope = "publish_stream,manage_pages";

            if (Request["code"] == null)
            {
                Response.Redirect(string.Format(
                    "https://graph.facebook.com/oauth/authorize?client_id={0}&redirect_uri={1}&scope={2}",
                    app_id, Request.Url.AbsoluteUri, scope));
            }
            else
            {
                Dictionary<string, string> tokens = new Dictionary<string, string>();

                string url = string.Format("https://graph.facebook.com/oauth/access_token?client_id={0}&redirect_uri={1}&scope={2}&code={3}&client_secret={4}",
                    app_id, Request.Url.AbsoluteUri, scope, Request["code"].ToString(), app_secret);

                HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;

                using (HttpWebResponse response = request.GetResponse() as HttpWebResponse)
                {
                    StreamReader reader = new StreamReader(response.GetResponseStream());

                    string vals = reader.ReadToEnd();

                    foreach (string token in vals.Split('&'))
                    {
                        //meh.aspx?token1=steve&token2=jake&...
                        tokens.Add(token.Substring(0, token.IndexOf("=")),
                            token.Substring(token.IndexOf("=") + 1, token.Length - token.IndexOf("=") - 1));
                    }
                }

                string access_token = tokens["access_token"];

                var client = new FacebookClient(access_token);

                client.Post("/me/feed", new { message = "markhagan.me video tutorial" });
            }
        }
    }
}

Answer 5

You need to grant the permission "publish_stream".

Answer 6

You need to ask the user for the publish_stream permission. In order to do this you need to add publish_stream to the scope in the oAuth request you send to Facebook. The easiest way to do all of this is to use the facebooksdk for .net which you can grab from codeplex. There are some examples there of how to do this with a desktop app.

Once you ask for that permission and the user grants it you will receive an access token which you can use to post to your page's wall. If you need to store this permission you can store the access token although you might need to ask for offline_access permission in your scope in order to have an access token that doesn't expire.