Re: Exception in CFileDialog - why?

From:
"Alexandre Grigoriev" <alegr@earthlink.net>
Newsgroups:
microsoft.public.vc.mfc
Date:
Mon, 19 Apr 2010 21:15:21 -0700
Message-ID:
<#pELiAE4KHA.4016@TK2MSFTNGP05.phx.gbl>
Creation of CFileDialog is very inexpensive operation. You don't gain
anything by reusing it. DoModal itself is much more expensive.

"Vanja" <Vanja@discussions.microsoft.com> wrote in message
news:BEF69A5E-CD82-46DB-A62B-9154164791CD@microsoft.com...

Hello,

Does someone know why the CFileDialog throws CInvalidArgException if
"recycled" (DoModal called the second time)? The problem happens only on
Vista und Windows 7, and only if using bVistaSyle==TRUE. Creating the
dialog
with bVistaStyle==FALSE solves the problem, but it's a poor solution.
Also,
if file filters are not used, no exception occurs.

Here's the code (more or less the same example like in MSDN):

  // szFilters is a text string that includes two file name filters:
  // "*.my" for "MyType Files" and "*.*' for "All Files."
  TCHAR szFilters[]= _T("MyType Files (*.my)|*.my|All Files (*.*)|*.*||");

  // Create an Open dialog; the default file name extension is ".my".
  CFileDialog fileDlg(TRUE, _T("my"), _T("*.my"),
     OFN_FILEMUSTEXIST | OFN_HIDEREADONLY, szFilters, NULL, 0,
/*bVistaStyle*/ TRUE);

  // first time -> ok
  fileDlg.DoModal();

  // second time -> not so ok (CInvalidArgException thrown)
  // If the dialog was created with szFilters==NULL, no problems.
  // If the dialog was created with bVistaStyle==FALSE, no problems.
  fileDlg.DoModal();

Stack at the point of exception (first-chance) is:

 mfc90ud.dll!AfxThrowInvalidArgException() Line 233
 mfc90ud.dll!CFileDialog::ApplyOFNToShellDialog() Line 388
 mfc90ud.dll!CFileDialog::DoModal() Line 706
 CommonDialog_Test.exe!CCommonDialog_TestDlg::OnBnClickedBtnOpentwice()
Line 142
 . . . .

I could easily circumvent the problem by always creating a fresh instance
of
CFileDialog. But since the file-browser is required many times in my
application, my intention was to create it once, re-use it and thus
improve
the reaction time.

Thanks in advance.

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