Custom user data for asp.net forms authentication

CustomIdentity.cs

    /// <summary>
    /// Extra user custom data
    /// </summary>
    public class UserIdentity
    {
        public int UserId { get; set; }
        public string Username { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
    }


    [Serializable]
    public class CustomIdentity : IIdentity
    {
        private System.Web.Security.FormsAuthenticationTicket ticket;
        private UserIdentity user;

        public CustomIdentity(System.Web.Security.FormsAuthenticationTicket ticket)
        {
            this.ticket = ticket;
            //deserialize the userdata back into user identity
            user = JsonSerializer.DeserializeFromString<UserIdentity>(ticket.UserData);
        }

        public string AuthenticationType
        {
            get { return "Custom"; }
        }

        public bool IsAuthenticated
        {
            get { return ticket != null; }
        }
        
        public string Username
        {
            get { return user.Username; }
        }
        public string FirstName
        {
            get { return user.FirstName; }
        }
        public string LastName
        {
            get { return user.LastName; }
        }
        public string Name
        {
            get { return user.Username; }
        }
        public int UserId
        {
            get { return user.UserId; }
        }

    }