This message returns the line number of the line that contains the character whose position (indexed from the beginning of the text) is specified by the wParam parameter.
| Parameter | Description |
| wParam | Contains the index value for the desired character in the text of the edit control (these index values are zero-based), or contains –1. | |
| lParam | Is not used. |
The return value is a line number. If wParam is –1, the number of the line that contains the first character of the selection is returned; otherwise, wParam contains the index (or position) of the desired character in the edit-control text, and the number of the line that contains that character is returned.