使用Facebook C＃SDK在登陆页面上获取AccessToken

Question

Coding Platform ASP.NET 4.0 WebForms

I have two pages that are relevant here

1. Login.aspx
2. LandingPage.aspx

On Login.aspx when I click an ImageButton, I redirect to Facebook site with the following code

protected void FacebookLoginButton_Click(object sender, ImageClickEventArgs e)
{
    try
    {
        Response.Redirect(GetFacebookLoginURL());
    }
    catch (System.Threading.ThreadAbortException)
    {
        throw;
    }
    catch (Exception err)
    {
        Elmah.ErrorSignal.FromCurrentContext().Raise(err);
    }
}

private string GetFacebookLoginURL()
{
    try
    {
        string baseURL = System.Configuration
            .ConfigurationManager
            .AppSettings["WebsiteURL"]
            .ToString();

        string[] extendedPermissions = new[] { 
            "publish_stream", 
            "offline_access" 
        };

        var oauth = new FacebookOAuthClient { 
            ClientId = FacebookContext.Current.AppId 
        };

        var parameters = new Dictionary<string, object>{
            { "response_type", "token" },
            { "display", "page" }
        };

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

            parameters["scope"] = scope.ToString();
        }
        parameters["redirect_uri"] = String.Format("{0}LandingPage.aspx", baseURL);
        return oauth.GetLoginUrl(parameters).OriginalString;
    }
    catch (Exception err)
    {
        Elmah.ErrorSignal.FromCurrentContext().Raise(err);
        return "";
    }
}

That part is working properly. But I am clueless on how to access the user info at the LandingPage which is my redirect_uri. Have tried this.

    FacebookOAuthClient cl = new FacebookOAuthClient(FacebookContext.Current);
    FacebookOAuthResult result = null; 
    string url = Request.Url.AbsoluteUri;

    // verify that there is a code in the url
    if (FacebookOAuthResult.TryParse(url, out result))
    {
        if (result.IsSuccess)                               
        {
            var accesstoken = result.AccessToken;
        }
        else
        {
            var errorDescription = result.ErrorDescription;
            var errorReason = result.ErrorReason;
        }
    }

But I doubt it wont work since I dont have window.hash.location at Server Side(Its not working anyway)

    var client = new FacebookClient(FacebookContext.Current);
    dynamic me = client.Get("me");
    string firstName = me.first_name;
    string lastName = me.last_name;
    string email = me.email;

Although I am not sure, getting the Access Token will solve my problem, won't it? This is the error I am getting.

(OAuthException) An active access token must be used to query information about the current user.

What am I doing wrong?

Answer 1

here's a sample of a standalone website using webforms. Check out Default.aspx.cs and Web.config . Please note that this sample could be modified for use with the latest source code and might not work with the latest release (5.0.3 beta).

Answer 2

I just recently did this implementation. To access "me", you need to have an Access Token.

The implementation is pretty straighforward, however, I will say that I found the major stumbling block for me was to make sure that my redirect_uri from my "Login.aspx" url matched the redirect_uri from my landing page.

Answer 3

It must be simple, but I dodnt get it. So I used the lesser used Facebook C# SDK by Facebook . I pretty much did what this blog suggested . Everything is fine now.