The CBN_CLOSEUP notification message is sent when the list box of a combo box has been closed. The parent window of the combo box receives this notification message through the WM_COMMAND message.
CBN_CLOSEUP
idComboBox = (int) LOWORD(wParam); // identifier of combo box
hwndComboBox = (HWND) lParam; // handle to combo box
If the user changed the current selection, the combo box also sends the CBN_SELCHANGE notification when the drop-down list closes. In general, you cannot predict the order in which notifications will be sent. In particular, a CBN_SELCHANGE notification message may occur either before or after a CBN_CLOSEUP notification message.
To execute a specific process each time the user selects a list item, you can handle either the CBN_SELCHANGE or CBN_CLOSEUP notification message. Typically, you would wait for the CBN_CLOSEUP notification before processing a change in the current selection. This can be particularly important if a significant amount of processing is required.
This notification message is not sent to a combo box that has the CBS_SIMPLE style.
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Requires version 1.0 or later.
Header: Declared in winuser.h.
Combo Boxes Overview, Combo Box Messages, CBN_DROPDOWN, CBN_SELCHANGE, WM_COMMAND