brandonc/statemachine

A simple, templated state machine class for .net

statemachine

A simple, templated state machine class for c#

Example

public enum OrderState
{
    Created,
    Ordered,
    Cancelled,
    Preparing,
    Shipped
};

public class Order
{
    public StateMachine<OrderState> Status { get; set; }

    public void Complete()
    {
        this.Status.State = OrderState.Ordered;
    }

    public void Cancel()
    {
        this.Status.State = OrderState.Cancelled;
    }

    public void Prepare()
    {
        this.Status.State = OrderState.Preparing;
    }

    public void Ship()
    {
        this.Status.State = OrderState.Shipped;
    }

    public Order()
    {
        // You could also subclass StateMachine<T> and encapsulate these details
        Status = new StateMachine<OrderState>(OrderState.Created);
        
        // Only transitions defined here are valid. Alternatively, you could call
        // ValidAny() to allow all state transitions
        Status.Valid(OrderState.Created,   OrderState.Ordered);
        Status.Valid(OrderState.Ordered,   new[] { OrderState.Cancelled, OrderState.Preparing });
        Status.Valid(OrderState.Preparing, OrderState.Shipped);

        // Enter transition events
        Status.DoWhenAny((status) =>
        {
            // Useful for writing a transition history log
            Debug.WriteLine("[{0}] Order Status => {1}", (DateTime.Now - new DateTime(1970, 1, 1, 0, 0, 0)).TotalMilliseconds, status);
        });

        // Or DoFollowingAny() for exit transitions
    }
}

Dynamic Events

If you're using .net 4.0, you can use dynamic binding in the style of rails:

Status.Transitions.Enter_Shipped((Action)delegate()
{
	Debug.WriteLine("Order Shipped!");
});

Status.Transitions.Exit_Ordered((Action)delegate()
{
	Debug.WriteLine("Order Processed!");
});