Begins a user-defined undo operation. All editing and fomatting changes made between BeginUndoAction and EndUndoAction belong to the undo operation. These changes are undone or redone in a single step. The specified user-defined name is available with the UndoActionName property.
[C#] public void BeginUndoAction(string actionName);
[Visual Basic] Public Sub BeginUndoAction(ByVal actionName As String)
Specifies the undo action's name. If an action name is not necessary, this parameter can be null or an empty string.