MDI for Visual Basic 6.0 Users
You can use both Visual Basic 6.0 and Visual Basic 2008 to create multiple-document interface (MDI) applications; however the techniques for creating them and some of their behaviors differ.
In Visual Basic 6.0, multiple-document interface (MDI) applications are created by adding an MDI form to a project and then setting the MDIChild property of any child forms.
Visual Basic 2008 does not have an MDI form; any form can be made into an MDI parent by setting the IsMdiContainer property to True.
Many of the properties and methods that applied to Visual Basic 6.0 MDI forms have changed in Visual Basic 2008. For more information, see MDIForm Object for Visual Basic 6.0 Users.
The behavior of MDI applications has also changed. In Visual Basic 6.0, an MDI application having a form that is not an MDI child does not end until that form is closed, even if the MDI parent is closed. In Visual Basic 2008, the application ends when the startup form is closed, regardless of any non-MDI forms in the application.