This message inserts a string into the list box. No sorting is performed.
| Parameter | Description |
| wParam | Contains an index to the position that will receive the string. If the wParam parameter is –1, the string is added to the end of the list. | |
| lParam | Points to the null-terminated string that is to be inserted. If the list box was created with an owner-draw style but without the LBS_HASSTRINGS style, the lParam parameter is an application-supplied 32-bit value that is stored by the list box instead of the pointer to the string. |
The return value is the index of the position at which the string was inserted. The return value is LB_ERR if an error occurs; the return value is LB_ERRSPACE if insufficient space is available to store the new string.