When an event occurs in a list box, the list box sends a notification message to the dialog box procedure of the owner window. List box notification messages are sent when a user selects, double-clicks, or cancels a list box item; when the list box receives or loses the keyboard focus; and when the system cannot allocate enough memory for a list box request. A notification message is sent as a WM_COMMAND message in which the low-order word of the wParam parameter contains the list box identifier, the high-order word of wParam contains the notification message, and the lParam parameter contains the control window handle.
A dialog box procedure is not required to process these messages; the default window procedure processes them.
An application should monitor and process the following list box notification messages.
| Notification message | Description |
|---|---|
| LBN_DBLCLK | The user double-clicks an item in the list box. |
| LBN_ERRSPACE | The list box cannot allocate enough memory to fulfill a request. |
| LBN_KILLFOCUS | The list box loses the keyboard focus. |
| LBN_SELCANCEL | The user cancels the selection of an item in the list box. |
| LBN_SELCHANGE | The selection in a list box is about to change. |
| LBN_SETFOCUS | The list box receives the keyboard focus. |