CB_GETCURSEL
wParam = 0; /* not used, must be zero */
lParam = 0; /* not used, must be zero */
An application sends a CB_GETCURSEL message to retrieve the index of the currently selected item, if any, in the list box of a combo box.
This message has no parameters.
The return value is the zero-based index of the currently selected item, or it is CB_ERR if no item is selected.
CB_SELECTSTRING, CB_SETCURSEL