The member functions for modifying and querying list boxes let you set values or find out the status of the control at any given time.

To know what a user is doing to a list box at run time, however, you have to respond to notification messages from the control.

There are only a few things a user can do with a list box: scroll through the list, click an item, and double-click an item. When the user does one of these things, Windows sends a list box notification message to the list box's parent window. Normally, you define notification-response member functions in the parent window object to handle notifications for each of the parent's controls.

The following table summarizes the most common list box notifications:

List box notification messages

Event response table macro	Description
EV_LBN_SELCHANGE	An item has been selected with a single mouse click.
EV_LBN_DBLCLK	An item has been selected with a double mouse click.
EV_LBN_SELCANCEL	The user has deselected an item.
EV_LBN_SETFOCUS	The user has given the list box the focus by clicking or double-clicking an item, or by using Tab. Precedes LBN_SELCHANGE notification.
EV_LBN_KILLFOCUS	The user has removed the focus from the list box by clicking another control or pressing Tab.

Here is a sample parent window object member function to handle an LBN_SELCHANGE notification:

DEFINE_RESPONSE_TABLE1(TLBoxWindow, TFrameWindow)
 EV_LBN_SELCHANGE(ID_LISTBOX, EvListBoxSelChange),
END_RESPONSE_TABLE;
 
void TLBoxWindow::EvListBoxSelChange()
{
 int index = ListBox->GetSelIndex();
 if (ListBox->GetStringLen(index) < 10) {
  char string[10];
 
ListBox->GetSelString(string, sizeof(string));
  MessageBox(string, "You selected:", MB_OK);
 }
}

See Also