The CDM_SETDEFEXT message sets the default filename extension for an Explorer-style Open or Save As common dialog box. The dialog box must have been created with the OFN_EXPLORER flag; otherwise, the message fails.
CDM_SETDEFEXT
wParam = 0;
lParam = (LPARAM) (LPSTR) pszext;
// corresponding macro
void CommDlg_OpenSave_SetDefExt(hdlg, pszext)
No return value.
Windows NT: Requires version 4.0 or later.
Windows: Requires Windows 95 or later.
Windows CE: Requires version 1.0 or later.
Header: Declared in commdlg.h.
Common Dialog Box Library Overview, Common Dialog Box Messages, GetOpenFileName, GetSaveFileName, OPENFILENAME