An application sends a WM_CLEAR message to an edit control or combo box to delete (clear) the current selection, if any, from the edit control.
WM_CLEAR wParam = 0; // not used; must be zero lParam = 0; // not used; must be zero
This message has no parameters.
This message does not return a value.
The deletion performed by the WM_CLEAR message can be undone by sending the edit control an EM_UNDO message.
To delete the current selection and place the deleted content on the clipboard, use the WM_CUT message.
When sent to a combo box, the WM_CLEAR message is handled by its edit control. This message has no effect when sent to a combo box with the CBS_DROPDOWNLIST style.