How to close the browser window from action in NW7 SP11 in web dynpro

Hi Experts.

I want to close the browser window throgh a button action on view. I followed many approaches but not working.

I gone throgh many thread in scn regarding ' How to close browser in web dynpro'. But in some cases a Blank window is appearing on action and in some cases error comes '  Parameters of exit plugs and suspened plugs must be of type STRING or TIHTTPNV  '.

With the below code Blank window browser is appearing :

I have declared a window out bound plug 'EXIT' type 'EXIT with interface 'checked'.

DATA: l_ref_MAIN_WINDOW TYPE REF TO IG_MAIN_WINDOW .
l_ref_MAIN_WINDOW =   wd_This->Get_Main_Window_Ctr( ).
  l_ref_MAIN_WINDOW->Fire_Exit_Plg(
).

Can any one tell me how to close the window browser in NW7 Service pack 11.