Check whether facebook user likes my app - vb.net

Question

I've read several sources now but did not find a solution: I'm using Facebook C# SDK with ASP.net 4 and VB.net 2010. I have a Facebook Canvas application. I'm using Canvas Auth.Authorize and it works fine. Now I want to know whether the currently logged in user already likes my app. How could I do that?
'SignedRequest' does not seem to work because according to Facebook Documentation "This field is only present if your app is being loaded within a Page Tab".
graph/user/likes is also not an option because I don't want to ask the user to grant access for my app to all his likes.
But the Facebook Plugin is able to differ whether the current user likes my app or not, so I'm quite optimistic that there is a way which I just did not find yet.
Many thanks!

Answer 1

You can use the graph API to call the users likes. Instead of requesting all of the likes simply request the single one you want.
https://graph.facebook.com/userId/likes/appId
If you the user has liked the page the result will return details about the page. For example:
{
"data": [
{
"name": "Microsoft Office Web Apps",
"category": "Software",
"id": "121883824529155",
"created_time": "2012-03-14T06:48:47+0000"
}
],
"paging": {
"next": "https://graph.facebook.com/me/likes/121883824529155?format=json&limit=5000&offset=5000&__after_id=121883824529155"
}
}
If the user has not liked the page you will receive empty data.
{
"data": [
]
}
With the Facebook C# SDK you would make this request as follows:
var client = FacebookClient("access_token_here");
dynamic result = client.Get('/me/appId');
if (result.data.Length == 1) {
// User has liked page
}