Q171978: INFO: Non-Modal Form Support in Visual Basic DLLs

Article: Q171978
Product(s): Microsoft Visual Basic for Windows
Version(s): 
Operating System(s): 
Keyword(s): kbGrpDSVB
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0 
- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0 
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SUMMARY
=======

Visual Basic 4.0 ActiveX DLLs (in-process ActiveX Servers) could display forms
modally only. Visual Basic versions 5.0 and later allow you to display forms
modally or in modeless form. When designing a ActiveX DLL, you have to take into
consideration whether the client application supports displaying modeless forms.

MORE INFORMATION
================

Modeless forms displayed by in-process components cannot function correctly
unless they can communicate with the client's message loop. Therefore, in-
process components created with Visual Basic can display modeless forms only in
client processes that support such communication.

The following applications support the display of modeless forms by in- process
components:

- Applications created with Visual Basic 5.0 or later.

- Microsoft Office 97 or later.

- Applications that have the Visual Basic Technology logo.(Those that license
  Visual Basic for Applications version 5.0 or later.)

Applications that do not support the display of modeless forms by in- process
components include:

- Applications created with earlier versions of Visual Basic.

- Earlier versions of Microsoft Office.

- Version 3.0 of Microsoft Internet Explorer.

To allow in-process components to detect at run time whether a client application
supports the display of modeless forms, Visual Basic provides the Boolean
NonModalAllowed property of the App object.

An in-process component should test this property before showing a modeless form.
If the value is True, the form can be shown vbModeless. If the value is False,
showing a modeless form will cause run-time error 369. The component should
degrade gracefully by showing the form vbModal instead.


For example:

     If App.NonModalAllowed Then
        Form1.Show vbModeless
     Else
        Form1.Show vbModal
     EndIf

Additional query words: kbVBp500 kbVBp600 kbVBp kbdsd kbDSupport kbNoKeyWord

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Keywords          : kbGrpDSVB 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600
Issue type        : kbinfo

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