BiomePainter.History.HistoryManager.Add C# (CSharp) Метод

        public void Add(IAction action)
        {
            if(action.GetType() == typeof(SelectionAction) && firstSelectionAction == null)
                firstSelectionAction = (SelectionAction)action;
            else if (action.GetType() == typeof(BiomeAction) && firstBiomeAction == null)
                firstBiomeAction = (BiomeAction)action;
            else if (action.GetType() == typeof(PopulateAction) && firstPopulateAction == null)
                firstPopulateAction = (PopulateAction)action;

            //ensure the first action of each type isn't lost when the redo stack is emptied
            if(firstSelectionAction != null && action != firstSelectionAction && redoStack.Contains(firstSelectionAction))
            {
                redoStack.Remove(firstSelectionAction);
                undoStack.AddLast(firstSelectionAction);
            }
            if (firstBiomeAction != null && action != firstBiomeAction && redoStack.Contains(firstBiomeAction))
            {
                redoStack.Remove(firstBiomeAction);
                undoStack.AddLast(firstBiomeAction);
            }
            if (firstPopulateAction != null && action != firstPopulateAction && redoStack.Contains(firstPopulateAction))
            {
                redoStack.Remove(firstPopulateAction);
                undoStack.AddLast(firstPopulateAction);
            }

            action.PreviousAction = GetPreviousAction(undoStack.Last, action.GetType());
            undoStack.AddLast(action);
            foreach (IAction a in redoStack)
                a.Dispose();
            redoStack.Clear();
        }