An undo group is a group of operations that is combined into a single undo operation.

Undo groups can be nested: New undo groups can be started within other undo groups. The number of EndUndoGroup(Object) calls need to match the number of BeginUndoGroup calls. All operations between the outer BeginUndoGroup and EndUndoGroup(Object) are combined and pushed onto the undo stack.

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