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IVBUndoUnit Object (Visio)

office 365 dev account|Last Updated: 6/12/2017
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The interface on an undo unit in Microsoft Visio. An undo unit encapsulates the information necessary to undo or redo a single action.


The default property of IVBUndoUnit is Description .

You can use the IVBUndoUnit interface in Microsoft Visual Basic for Applications (VBA) or Microsoft Visual Basic to create your own undo units for the Visio undo manager. To create an undo unit, you must implement this interface, along with all of its public procedures, in a class module that you insert into your project.

For more information about using the IVBUndoUnit interface to create undo units, search for "creating undo units" on MSDN, the Microsoft Developer Network.

IVBUndoUnit methods and properties in VTable order

** IUnknown Methods**** Description**
QueryInterfaceReturns a pointer to a specified interface.
AddRefIncrements the reference count.
ReleaseDecrements the reference count.
IVBUndoUnit MethodsDescription
DoInstructs the undo unit to carry out its action.
OnNextAddNotifies the last undo unit in the collection that a new unit has been added.
IVBUndoUnit PropertiesDescription
DescriptionRead-only. Describes the undo action.
UnitTypeCLSIDRead-only. Returns the CLSID and a type identifier for the undo unit.
UnitTypeLongRead-only. Returns a Long that can be used to identify the undo unit.
UnitSizeSize in bytes. Used to measure how much memory undo information is using.
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