FormsAuthentication custom user data

FormsAuthenticationService.cs

    public class FormsAuthenticationService : IFormsAuthenticationService
    {
        public void SignIn(UserIdentity user, bool createPersistentCookie)
        {
            //UserData is stored as json
            string userData = JsonSerializer.SerializeToString<UserIdentity>(user);

            FormsAuthenticationTicket authTicket = new
                FormsAuthenticationTicket(1, //version
                                          user.UserId.ToString(), // user name
                                          DateTime.Now,             //creation
                                          DateTime.Now.AddMinutes(30), //Expiration
                                          createPersistentCookie, userData); //storing the json data

            string encTicket = FormsAuthentication.Encrypt(authTicket);

            var cookie = new HttpCookie(FormsAuthentication.FormsCookieName, encTicket)
                             {
                                 Expires = authTicket.Expiration,
                                 Path = FormsAuthentication.FormsCookiePath
                             };

            if (HttpContext.Current != null)
            {
                HttpContext.Current.Response.Cookies.Add(cookie);
            }

        }

        public void SignOut()
        {
            FormsAuthentication.SignOut();
        }
    }