An application sends a CB_RESETCONTENT message to remove all items from the list box and edit control of a combo box.
CB_RESETCONTENT
wParam = 0; // not used; must be zero
lParam = 0; // not used; must be zero
This message has no parameters.
This message always returns CB_OKAY.
If you create the combo box with an owner-drawn style but without the CBS_HASSTRINGS style, the owner of the combo box receives a WM_DELETEITEM message for each item in the combo box.
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, CB_DELETESTRING, WM_DELETEITEM