The File Dialog - MFC

Save as a file with a specific extension

2025-10-31

Written by: xiaobin

Use the CFileDialog to customize the file extension, title, and initial directory.

explicit CFileDialog(
    BOOL bOpenFileDialog,
    LPCTSTR lpszDefExt = NULL,
    LPCTSTR lpszFileName = NULL,
    DWORD dwFlags = OFN_HIDEREADONLY | OFN_OVERWRITEPROMPT,
    LPCTSTR lpszFilter = NULL,
    CWnd* pParentWnd = NULL,
    DWORD dwSize = 0,
    BOOL bVistaStyle = TRUE);

• bOpenFileDialog

The parameter that specifies what type of dialog box to create.

Set it to TRUE to construct a File Open dialog box. 
Set it to FALSE to construct a File Save As dialog box.

• lpszDefExt
  The default file name extension.
• lpszFileName
  The initial file name that appears in the Filename box.
• dwFlags

Use OFN macro combinations.

• lpszFilter
  A series of string pairs that specify filters you can apply to the file.
• pParentWnd
  A pointer to the parent or owner window of the file dialog box.
• option
  These parameters can be omitted.

OFN macros

• OFN_HIDEREADONLY

Hides the Read Only check box.

• OFN_OVERWRITEPROMPT

Causes the Save As dialog box to generate a message box if the selected file already exists. The user must confirm whether to overwrite the file.

For a description of these flags, see the OPENFILENAME structure in the Windows SDK.

example

strFileName.Format("%d%d%d%d%d%d", nYear, nMonth, nDay, nHour, nMinute, nSecond);
strFileName = "D" + strFileName + ".rtf";

    CFileDialog fSaveDialog(FALSE,                  // Set to TRUE to construct a File Open dialog box or 
                                                    // FALSE to construct a File Save As dialog box.
        ".rtf", 
        strFileName, 
        OFN_HIDEREADONLY|OFN_OVERWRITEPROMPT, 
        "Serial Comm Data (*.rtf)|*.rtf|Text (*.txt)|*.txt||", 
        this);
    fSaveDialog.m_pOFN->lpstrTitle = "Serial Comm Data File (Save As...)";
    fSaveDialog.m_pOFN->lpstrInitialDir = "D:";

    if (fSaveDialog.DoModal() == IDOK)
        strPathName = fSaveDialog.GetPathName();
    else
        return;

m_pOFN

Customize the dialog box title and the initial directory.

    fSaveDialog.m_pOFN->lpstrTitle = "Serial Comm Data File (Save As...)";
    fSaveDialog.m_pOFN->lpstrInitialDir = "D:";

GetPathName

The path of the filename includes the file’s title plus the entire directory path.

Ref

• The File Dialog
• MFC File Processing: The File Dialog Box