AppFabric Topic Subscription

Question

I am trying to assemble a simple AppFabric Topic whereby messages are sent and received using the SessionId. The code does not abort, but brokeredMessage is always null. Here is the code:

// BTW, the topic already exists

var messagingFactory = MessagingFactory.Create(uri, credentials);
var topicClient = messagingFactory.CreateTopicClient(topicName);
var sender = topicClient.CreateSender();
var message = BrokeredMessage.CreateMessage("Top of the day!");
message.SessionId = "1";
sender.Send(message);

var subscription = topic.AddSubscription("1", new SubscriptionDescription { RequiresSession = true});
var mikeSubscriptionClient =  messagingFactory.CreateSubscriptionClient(subscription);
var receiver = mikeSubscriptionClient.AcceptSessionReceiver("1");
BrokeredMessage brokeredMessage;
receiver.TryReceive(TimeSpan.FromMinutes(1), out brokeredMessage); // brokeredMessage always null

Answer 1

You have two problems in your code:

1. You create a subscription AFTER you send the message. You need to create a subscription before sending, because a subscription tells the topic to, in a sense, copy, the message to several different "buckets".

2. You are using TryReceive but are not checking for its result. It returns true, if a message was received, and false if not (e.g. Timeout has occured).

I am writing my sample application and will post it on our blog today. I will post the link here as well. But until then, move the subscription logic to before sending the message, and the receiver after it and you will start seeing results.

Update: As promised, here is the link to my blog post on getting started with AppFabric Queues, Topics, Subscriptions.