When a user chooses an item in a list, the primary notification an application receives is a WM_CONTROL message, with the LN_ENTER control code sent to the owner window of the list. Within the window procedure for the owner window, the application responds to the LN_ENTER control code by querying the list box for the current selection (or selections, in the case of an LS_MULTIPLESEL or LS_EXTENDEDSEL list box).

The LN_ENTER control code notifies the application that the user has selected a list item. A WM_CONTROL message with an LN_SELECT control code is sent to the list-box owner whenever a selection in a list changes, such as when a user moves the mouse pointer up and down a list while pressing the mouse button. In this case, items are selected but not yet chosen. An application can ignore LN_SELECT control codes when the selection changes, responding only when the item is actually chosen. Or an application can use LN_SELECT to display context-dependent information that changes rapidly with each selection made by the user.