Question

I’m just getting started with NServiceBus and I’ve got a very basic implementation up and running – much like the PubSub sample application.

What I want to do is to send some information when a subscriber subscribes.

For example, lets say I have a database with products that are categorized. My publisher will check the database every N seconds and will send messages when a new product is added to the database.

But each subscriber is only interested in a particular category and I want to send that category when they subscribe so that the publisher knows the check the database for new products in that category.

The categories are dynamic, so I can’t create different messages for the different categories. So for that reason I assume that all the subscribers have to subscribe to the same published IMessage.

NOTE: I do also wish to use this information to then filter the messages NServiceBus sends to subscribers, but I thought I would post that as a separate question.

Answer 1

You can implement the IAuthorizeSubscriptions interface to get a callback at the publisher when a subscriber requests to subscribe. If you wanted to include some additional meta-data in the subscription request, you’ll need to use Bus.OutgoingHeaders – then you can look at that info at the publisher and decided what to do with it.