php - Inject doctrine in a formbuilder class -

i tryin inject entity manager in formbuilder class. error :

catchable fatal error: argument 1 passed pdb\backend\admin\relationmanagementbundle\form\search\searchform::__construct() must instance of doctrine\orm\entitymanager, none given.

services:     my_service:         class:      pdb\backend\admin\relationmanagementbundle\form\search\searchform         arguments:               entitymanager: "@doctrine.orm.entity_manager" 

my constructor :

class searchform extends abstracttype {  protected $entitymanager;  public function __construct(entitymanager $entitymanager) {     $this->entitymanager = $entitymanager; } 

in controller

public function showaction($id,$tab)     { ...         $em = $this->getdoctrine()->getmanager();          $form    = $this->createform(new pdb\backend\admin\relationmanagementbundle\form\search\searchform($em), $entity);   .. } 

then in form

class searchform extends abstracttype {  protected $entitymanager;  public function __construct(entitymanager $entitymanager) {     $this->entitymanager = $entitymanager; }