Facebook.CanvasAuthContext.ValidateSession C# (CSharp) Method

        Session ValidateSession(JsonObject data)
        {
            if (!data.IsDictionary)
                throw new ArgumentException("Should be a dictionary", "data");

            Session session = null;
            if (data.IsDictionary
                && data.Dictionary.ContainsKey("uid")
                && data.Dictionary.ContainsKey("access_token")
                && data.Dictionary.ContainsKey("sig"))
            {
                string expectedSignature = GenerateSignature(data);
                if (expectedSignature != data.Dictionary["sig"].String)
                    throw new FacebookApiException("Canvas", "Unexpected signature");

                return Session.FromJsonObject(data);
            }

            return session;
        }