fsm.cs

using System;

public interface FSM<S,E,T> {
	public void defineTransition(S oldState, E event, S newState, Action<T> action);
	public void consumeEvent(E event);
		
	public S getState();
	public void setState(S newState);
}

public class Behaviours {
	public static FSM<Order, OrderEvents, OrderStates> CreateOrderFsm(Order order);
}

OrderEvents nextEvent = new DeliveryEvent();
Order order = getOrderById(id);
var fsm = Behaviours.CreateOrderFsm(order, nextEvent);
fsm.consumeEvent(nextEvent);
order.save();