http://www.nuget.org/packages/Facebook.CSharp.SDK/からSDKをダウンロードします
var config = new Dictionary<string, object>();
//your application id and secret from https://developers.facebook.com/apps
config.Add("appId", "3955.......");
config.Add("secret", "4c1d...............");
config.Add("fileUpload", true); //optional
FacebookClient client = new FacebookClient(config);
var fields = client.getSignedRequest()["page"] as Dictionary<string, object>;
var graphApiCall = new FacebookGraphApiRequest();
graphApiCall.Method = FacebookApiMethodType.GET;
graphApiCall.Path = fields["id"];
graphApiCall.Params = null;
//this is the json string that holds all the json string.
Response.Write(client.api(graphApiCall));