GoCoinAPI.Client.getToken C# (CSharp) Method

    public string getToken() {
        if (this.token == null) {
            if ( HttpContext.Current.Session["gocoin_access_token"] !=null) {
                this.token = HttpContext.Current.Session["gocoin_access_token"].ToString();
            }
        }
        return this.token;
    }

        protected void Page_Load(object sender, EventArgs e)
        {
           // getauthorizeapi();

           Client client = new Client("your api key");
            var invoice1 = new Invoices
                {
                    price_currency = "BTC",
                    base_price = 134.00f,
                    base_price_currency = "USD",
                    confirmations_required = 6,
                    notification_level = "all",
                    callback_url = "https://www.example.com/gocoin/callback",
                    redirect_url = "https://www.example.com/redirect"
                };

            GoCoinAPI.Invoices inv =  client.api.invoices.create("your merchant id",invoice1);
            string token = client.getToken();
                LitAccessToken.Text = token;
             Boolean b_auth = client.authorize_api();
            if (b_auth)
            {
                GoCoinAPI.User currentuser = new GoCoinAPI.User();
                currentuser = client.api.user.self();
                Response.Write(" User Calls");
                Response.Write("</br>");
                Response.Write("+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++");
                Response.Write("</br>");
                Response.Write("</br>");
                Response.Write(" User get");
                Response.Write("</br>");
                Response.Write(SerializeJson(client.api.user.get(currentuser.id)));
                Response.Write("</br>");
            }
            else
            {
                Response.Redirect("Error in getting the User Data", false);

            }
        }