This message is sent when the user chooses the End Session command. If any application returns zero, the session is not ended. Windows stops sending WM_QUERYENDSESSION messages as soon as one application returns zero, and sends WM_ENDSESSION messages, with the wParam parameter set to zero, to any applications that have already returned nonzero.
| Parameter | Description |
| wParam | Is not used. | |
| lParam | Is not used. |
The return value is nonzero if the application can be conveniently shut down. Otherwise, it is zero.
The DefWindowProc function returns nonzero.