Call this method to push an UndoableOperation on the undostack. However, the operation will be only stored if the undo group contains a non-optional operation. Use this method to store the caret position/selection on the undo stack to prevent having only actions that affect only the caret and not the document.

public void PushOptional(
	IUndoableOperation operation
)

Public Sub PushOptional ( _
	operation As IUndoableOperation _
)

public:
void PushOptional(
	IUndoableOperation^ operation
)