void PerformAddUser(string username)
    {
        message       = "Finding user...";
        ButtonEnabled = false;

        KiiUser.FindUserByUserName(username, (KiiUser user, Exception e) =>
        {
            if (e != null)
            {
                ButtonEnabled = true;
                message       = "Failed to find user " + e.Message;
                return;
            }

            message = "Adding user....";

            currentGroup.AddUser(user);
            currentGroup.Save((KiiGroup group, Exception e2) =>
            {
                ButtonEnabled = true;
                if (e2 != null)
                {
                    message = "Failed to add user " + e.ToString();
                    return;
                }
                message = "Add user succeeded";
            });
        });
    }