EM_SETREADONLY
wParam = (WPARAM) (BOOL) fReadOnly; /* read-only flag */
lParam = 0L; /* not used, must be zero */
An application sends an EM_SETREADONLY message to set the read-only state of an edit control.
fReadOnly
Value of wParam. Specifies whether to set or remove the read-only state of the edit control. A value of TRUE sets the state to read-only; a value of FALSE sets the state to read/write.
The return value is nonzero if the operation is successful, or it is zero if an error occurs.
When the state of an edit control is set to read-only, the user cannot change the text within the edit control.
This example sets the state of an edit control to read-only:
SendDlgItemMessage
(hdlg, IDD_EDIT, EM_SETREADONLY, TRUE, 0L);