web dynpro for abap & sap protal protect mode

hi:all

  I'm trying to implement the Work Protect Mode to work in a Netweaver 7.4 Scenario and web dynpro for abap.but it 'failed

  I have writed the code in web dynpro for abap and modifyed com.sap.portal.epcf.loader, and setting workprotect.mode.default to 2  in sap protal .

the code in wda:

data L_COMPONENTCONTROLLER type ref to IG_COMPONENTCONTROLLER .

data L_API_COMPONENTCONTROLLER type ref to IF_WD_COMPONENT.

data L_PORTAL_MANAGER type ref to IF_WD_PORTAL_INTEGRATION.

L_COMPONENTCONTROLLER =  WD_THIS->GET_COMPONENTCONTROLLER_CTR( ).

L_API_COMPONENTCONTROLLER = L_COMPONENTCONTROLLER->WD_GET_API( ).

L_PORTAL_MANAGER = L_API_COMPONENTCONTROLLER->GET_PORTAL_MANAGER( ).

call method L_PORTAL_MANAGER->SET_WORK_PROTECT_MODE
exporting
MODE  = 'BOTH'.

call method L_PORTAL_MANAGER->SET_APPLICATION_DIRTY_FLAG
exporting
DIRTY_FLAG = abap_true.

   how I should to do?

  thanks!!