A dialog box procedure can send messages to a list box to add, delete, examine, and change list box items. For example, a dialog box procedure could send an LB_ADDSTRING message to a list box to add an item, and an LB_GETSEL message to determine whether the item is selected. Other messages set and retrieve information about the size, appearance, and behavior of the list box. For example, the LB_SETHORIZONTALEXTENT message sets the scrollable width of a list box. A dialog box procedure can send any message to a list box by using the SendMessage or SendDlgItemMessage function.
A list box item is often referenced by its index, an integer that represents the item's position in the list box. The index of the first item in a list box is 0, the index of the second item is 1, and so on.
The following table describes how the predefined list box procedure responds to list box messages.
| Message | Response |
|---|---|
| LB_ADDFILE | Inserts a file into a directory list box filled by the DlgDirList function and retrieves the list box index of the inserted item. |
| LB_ADDSTRING | Adds a string to a list box and returns its index. |
| LB_DELETESTRING | Removes a string from a list box and returns the number of strings remaining in the list. |
| LB_DIR | Adds a list of filenames to a list box and returns the index of the last filename added. |
| LB_FINDSTRING | Returns the index of the first string in the list box that matches a given prefix. |
| LB_FINDSTRINGEXACT | Returns the index of the string that is equivalent to or prefixed by a given prefix. |
| LB_GETANCHORINDEX | Returns the index of the item that the mouse last selected. |
| LB_GETCARETINDEX | Returns the index of the item that has the focus rectangle. |
| LB_GETCOUNT | Returns the number of items in the list box. |
| LB_GETCURSEL | Returns the index of the currently selected item. |
| LB_GETHORIZONTALEXTENT | Returns the scrollable width, in pixels, of a list box. |
| LB_GETITEMDATA | Returns the 32-bit value associated with the given item. |
| LB_GETITEMHEIGHT | Returns the height, in pixels, of an item in a list box. |
| LB_GETITEMRECT | Retrieves the client coordinates of the given list box item. |
| LB_GETLOCALE | Retrieves the locale of the list box. The high-order word contains the country code and the low-order word contains the language identifier. |
| LB_GETSEL | Returns the selection state of a list box item. |
| LB_GETSELCOUNT | Returns the number of selected items in a multiple-selection list box. |
| LB_GETSELITEMS | Creates an array of the indexes of all selected items in a multiple-selection list box and returns the total number of selected items. |
| LB_GETTEXT | Retrieves the string associated with a given item and the length of the string. |
| LB_GETTEXTLEN | Returns the length, in characters, of the string associated with a given item. |
| LB_GETTOPINDEX | Returns the index of the first visible item in a list box. |
| LB_INITSTORAGE | Allocates memory for the specified number of items and their associated strings. |
| LB_INSERTSTRING | Inserts a string at a given index in a list box. |
| LB_ITEMFROMPOINT | Retrieves the zero-based index of the item nearest the specified point in a list box. |
| LB_RESETCONTENT | Removes all items from a list box. |
| LB_SELECTSTRING | Selects the first string it finds that matches a given prefix. |
| LB_SELITEMRANGE | Selects a given range of items in a list box. |
| LB_SELITEMRANGEEX | Selects a given range of items if the index of the first item in the range is less than the index of the last item in the range. Cancels the selection in the range if the index of the first item is greater than the last. |
| LB_SETANCHORINDEX | Sets the item that the mouse last selected to a given item. |
| LB_SETCARETINDEX | Sets the focus rectangle to a given list box item. |
| LB_SETCOLUMNWIDTH | Sets the width, in pixels, of all columns in a list box. |
| LB_SETCOUNT | Sets the number of items in a list box. |
| LB_SETCURSEL | Selects a given list box item. |
| LB_SETHORIZONTALEXTENT | Sets the scrollable width, in pixels, of a list box. |
| LB_SETITEMDATA | Associates a 32-bit value with a list box item. |
| LB_SETITEMHEIGHT | Sets the height, in pixels, of an item or items in a list box. |
| LB_SETLOCALE | Sets the locale of a list box and returns the previous locale identifier. |
| LB_SETSEL | Selects an item in a multiple-selection list box. |
| LB_SETTABSTOPS | Sets the tab stops to those specified in a given array. |
| LB_SETTOPINDEX | Scrolls the list box so the specified item is at the top of the visible range. |