ahmetkucukoglu

public class DeliveredState : ShipmentState
{
    public override string ToString() => nameof(DeliveredState);
}

ahmetkucukoglu

public class OutForDeliveryState : ShipmentState
{
    public override void Delivered(Shipment shipment)
    {
        Console.WriteLine("The cargo has been delivered.");

        shipment.MoveTo(new DeliveredState());
    }

    public override void NotDelivered(Shipment shipment)

ahmetkucukoglu

public class CustomsClearedState : ShipmentState
{
    public override void OutForDelivery(Shipment shipment)
    {
        Console.WriteLine("The cargo is out for delivery.");

        shipment.MoveTo(new OutForDeliveryState());
    }
    
    public override string ToString() => nameof(CustomsClearedState);

ahmetkucukoglu

public class InCustomsState : ShipmentState
{
    public override void CustomsCleared(Shipment shipment)
    {
        Console.WriteLine("Customs clearance procedures have been completed.");
    
        shipment.MoveTo(new CustomsClearedState());
    }
    
    public override string ToString() => nameof(InCustomsState);

ahmetkucukoglu

public class InTransitState : ShipmentState
{
    public override void InCustoms(Shipment shipment)
    {
        Console.WriteLine("The cargo has arrived at customs.");

        shipment.MoveTo(new InCustomsState());
    }
    
    public override string ToString() => nameof(InTransitState);

ahmetkucukoglu

public class OrderPlacedState : ShipmentState
{
    public override void InTransit(Shipment shipment)
    {
        if (shipment.FromCountry == "TR")
        {
            Console.WriteLine(GetInvalidMessage(nameof(InTransit), shipment.State));
            return;
        }

ahmetkucukoglu

public abstract class ShipmentState
{
    public virtual void InTransit(Shipment shipment)
    {
        Console.WriteLine(GetInvalidMessage(nameof(InTransit), shipment.State));
    }

    public virtual void InCustoms(Shipment shipment)
    {
        Console.WriteLine(GetInvalidMessage(nameof(InCustoms), shipment.State));

ahmetkucukoglu

public class Shipment
{
    public Guid OrderId { get; private set; }
    public string FromCountry { get; private set; }
    public string ToAddress { get; private set; }
    public ShipmentStatuses Status { get; private set; }
    public int DeliveryAttempts { get; internal set; }

    public Shipment(Guid orderId, string fromCountry, string toAddress)
    {

ahmetkucukoglu

var product = new Product
{
    Id = 1453,
    Stock = 0
};

var productService = new ProductService();
productService.Attach(new ProductStockObserver());

product.Stock = 10;

ahmetkucukoglu

public class ProductService : ObservableProduct
{
    public void UpdateStock(Product product)
    {
        //TODO Save product
        Notify(new ProductObserverArgs());
    }
}