How to get the facebook page id in an iframe app (C#)

I've created a simple facebook iframe app to be used as a tab on pages. It all works fine but I now need to get the id of the page that using the tab so I can display information particular to that page.

I've seen in the documentation that there's a value called "ProfileId" in the signedrequest and that should be the id of the page which is what I'm looking for but everytime I try to use the signedrequest I run into problems so I obviously don't understand what I need to do.

Can some开发者_如何学运维one explain how I can get the page id? I don't want the user to have to authorize the app as I'm not interested in any of their information I just want the id of the page that the tab is appearing on.

<?php

include "facebook.php"; //Facebook PHP SDK 

$app_id = "APP_ID_HERE"; // Your application id

$app_secret = "APP_SECRET_HERE"; // Your application secret

$facebook = new Facebook(array(
'appId' => $app_id,
'secret' => $app_secret,
'cookie' => true
));

$signedrequest = $facebook->getSignedRequest();

$page_id = $signedrequest["page"]["id"];
$is_admin = $signedrequest["page"]["admin"];
$is_liked = $signedrequest["page"]["liked"];

echo "Page id: ". $page_id;

?>

You can use the information in FacebookWebContext.Current.SignedRequest.Data:

if (FacebookWebContext.Current.SignedRequest != null)
{
  dynamic data = FacebookWebContext.Current.SignedRequest.Data;
  if (data.page != null)
  {
    var pageId = (String)data.page.id;
    var isUserAdmin = (Boolean)data.page.admin;
    var userLikesPage = (Boolean)data.page.liked;
  }
  else
  {
    // not on a page
  }
}