This code specifies that the user has double-clicked a button. The control's parent window receives this code through a WM_COMMAND message from a button control.
| Parameter | Description |
| wParam | Specifies the control ID. | |
| lParam | Contains a handle that identifies the button control in its low-order word and the BN_DOUBLECLICKED notification code in its high-order word. |
This code applies to buttons with the BS_RADIOBUTTON and BS_OWNERDRAW styles only.