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InvisibleApp.AddUndoUnit Method (Visio)

office 365 dev account|Last Updated: 6/12/2017
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Adds an object that supports the IOleUndoUnit or IVBUndoUnit interface to the Microsoft Visio undo queue.


expression . AddUndoUnit( pUndoUnit )

expression A variable that represents an InvisibleApp object.


NameRequired/OptionalData TypeDescription
pUndoUnitRequired[UNKNOWN]A reference to an object that supports the IOleUndoUnit or IVBUndoUnit interface.

Return Value



For information about implementing the IOleUndoUnit interface on your object, see the Microsoft Platform SDK on MSDN, the Microsoft Developer Network. For information about implementing the IVBUndoUnit interface, see Developing Microsoft Visio Solutions on MSDN.


The following procedure shows how to use the AddUndoUnit method to add an object to the Visio undo queue. When a shape is added to the active document, the procedure checks to see if it was added as a result of an undo or redo action, and if not, it adds an Undo unit.

This procedure is a member of class clsParticipateInUndo , which is defined in one of two related class modules in the Code Samples Library in the Visio SDK, and is not intended to be run independently. (The other class module defines class clsVBUndoUnits .) For more information on these class modules, see the Visio SDK on MSDN.

Private Sub mvsoDocument_ShapeAdded(ByVal vsoShape As IVShape) 

 Dim VBUndoUnit As clsVBUndoUnits 

 On Error GoTo mvsoDocument_ShapeAdded_Err 

 If Not (mvsoApplication Is Nothing) Then 

 If Not msvoApplication.IsUndoingOrRedoing Then 

 'Increment the count of undoable actions. 
 Debug.Print "Original Do: GetModuleVar = " &; GetModuleVar 

 'Instantiate clsVBUndoUnit, a 
 'class that implements Visio.IVBUndoUnit. 
 Set VBUndoUnit = New clsVBUndoUnits 

 'Pass the current instance of the class 
 'of which this procedure is a member, 
 'clsParticipateInUndo, to the Undo unit. 
 VBUndoUnit.SetModelObject Me 

 'Add an Undo unit. 
 mvsoApplication.AddUndoUnit VBUndoUnit 

 End If 

 End If 

Exit Sub 


 MsgBox Err.Description 

End Sub
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