protected function BeforeInit()
    {
        $this->user = User::Schema()->ByID(Request::GetData('user'));
        if (!$this->user || !self::Guard()->Allow(BackendAction::AssignGroups(), $this->user))
        {
            //TODO: Error message
            Response::Redirect(BackendRouter::ModuleUrl(new UserList()));
        }
        return parent::BeforeInit();
    }