Configuration "TopicName"

What is a TopicName?

A TopicName, or as we will refer to it in the rest of this document as the Topic, is an endpoint that a subscription belongs too.

If you think of the Windows Azure Service Bus Namespace as a Class, a Topic would be like registering to a common event on the class.

Let's say you have a NewOrder message:

public class NewOrder {

    public string OrderId {get;set}

    public decimal Total {get;set;}
}

And you had a topic called Order. That topic would look like this if you were coding an event:

public class OrderTopic {

    //When you create a subscription, it would be like created a new delegate against this event.
    public event Action<NewOrder> NewOrderCreated;

    //Calling this method is the same as Publishing a message to the Service Bus.
    public static void NotifySubscribers(NewOrder order) {
        if (NewOrderCreated != null) {
            NewOrderCreated(order);
        }
    }
}

When you create a class that implements IHandleMessages, the framework will automatically create a unique subscription for you in the declared topic for the message NewOrder. When a publisher sends a message to the topic, this subscription will automatically get a copy.

[MessageHandlerConfiguration(
    DeadLetterAfterMaxRetries=true, 
    MaxRetries = 2,
    PauseTimeIfErrorWasThrown = 15000,
    Singleton = true)]
public class TestMessageSubscriber : IHandleMessages<NewOrder> {

    static Logger logger = LogManager.GetCurrentClassLogger();

    public void Handle(IReceivedMessage<NewOrder> message) {
        logger.Info("TestMessageSubscriber Message received: {0} {1}", message.Message.Value, message.Message.MessageId);
    }
}

If you do not set the TopicName, every application that registers to the same Namespace will all be part of the same Topic.