BUG: Modal Dialog in Terminate Causes Lockup on Windows 95/98

ID: Q149036

The information in this article applies to:

Professional and Enterprise Editions of Microsoft Visual Basic for Windows, 16-bit only, version 4.0

SUMMARY

Displaying a modal dialog in the Terminate event of a class module can cause a lockup of the server providing the class and any clients. This happens with the 16-bit version of Visual Basic 4.0 on the Windows 95 and Windows 98 operating systems and can be demonstrated by the ds.vbp and thingtst.vbp samples in the oleserv sample directory.

STATUS

Microsoft has confirmed this to be an issue in the Microsoft products listed at the beginning of this article.

WORKAROUND

Do not show any modal dialogs in the Terminate event of a class. Showing any modal dialogs, including message boxes, is not recommended in either the Initialize or Terminate events of a class module because it can interfere with the creation and/or termination of objects. Both client and server are halted until the modal dialog is dismissed.

MORE INFORMATION

Steps to Reproduce Behavior

1. Start two instances of Visual Basic 4.0, 16-bit, on Windows 95. Load the

   ds.vbp sample located in the \vb4\samples\oleserv directory and click F5
   to start the server application.

2. Switch to the other running instance of VB4 16 and load the thingtst.vbp

   sample, which is also located in the \vb4\samples\oleserv directory. Say
   yes to the Could not create reference dialog box if it appears. The
   instance of the thing server running in the IDE has changed the registry
   so that it is used instead of any previously compiled instances of
   ds.exe. The references need to be changed in the client so this is taken
   into account.

3. On the Tools menu, choose References to show the References dialog box.

   Find the MISSING: Demonstration OLE Server entry and clear it. Close the
   dialog by clicking OK. Reopen the References dialog and check the
   Demonstration OLE Server entry.

4. Run the client application and enter a name for the Form Thing. Click

   OK, then click OK again to dismiss the message box shown in the
   Initialize event.

5. Click the New Form Thing button to set the old object reference to

   nothing and create a new instance of the Form Thing class. The Thing
   Terminate modal dialog box displays, but no longer responds to the
   mouse. The client and server are locked up at this point. The server
   can be shut down with the Close Program dialog (CTRL+ALT+DELETE and
   End Task).

Additional query words: kbVBp400bug kbVBp kbDSupport kbdsd kbNoKeyWord

Keywords          : kbVBp400bug 
Version           : 4.00
Platform          : NT WINDOWS
Issue type        : kbbug

Last Reviewed: November 11, 1998