Question

I have a WCF client, that asks for order confirmation and WCF service with two methods:

1) UpdateOrder – updates order data in database (UpdateOrder call comes from external service)
2) GetConfirmationResult – which holds return of result till order status will change from pending to something else.

Question is, how to make notification from UpdateOrder to GetConfirmationResult, that order status has changed, in WCF?

Update: would be best, if I could leave InstanceContextMode as Per-Call.

Update 2: Let’s say possible order statuses are Pending, Confirmed, Rejected. ConfirmOrder may change order status to Confirmed or Rejected, GetConfirmationResult should not return result until it is changed by Confirm order.

Update 3: I’ve changed image with sequence to display whole stack.

Answer 1

At the moment I’ve solved it using EventWaitHandle – not sure if it is the best way, but it looks quite clean, nicely supports timeout and is quite testable.

public class TestClass 
{
    public static event OrderUpdateHandler UpdatedOrder;

    public void UpdateData(Order order) 
    {
        // ...

        OnOrderUpdated(args);
    }

    public Order GetConfirmedOrder(int id, TimeSpan waitToConfirm) 
    {
        var order = GetOrderFromDatabase();

        if (order.Status == OrderStatus.Pending) 
        {
             var eventHandle = new EventWaitHandle(false, EventResetMode.AutoReset);

             UpdatedOrderHandler waiter = (s, e) =>
             {
                if (e.Order.Id == id)
                {
                    order = e.Order;
                    eventHandle.Set();
                }
            };

            UpdatedOrder += waiter;

            if (!eventHandle.WaitOne(waitToConfirm))
            {                
                return order;
            }

            OrderUpdated -= waiter;
        }

        return order;
    }
}