I’ve just uploaded a new release (v1.1) of my MSMQ Activities for Windows Workflow Foundation. This release does a few general fixes and polishes a few things here and there, but the largest change is a modification of the MsmqListenerService runtime service used by the MsmqReceiveActivity to listen to the MSMQ queues. This change is aimed at improving the situation I talked about on this past entry . Basically, this is something that will be very handy to ensure the activities work even when the hosting process dies unexpectedly and is restarted. As part of this release, a new interface is introduced in the component: IMsmqSubscriptionPersistenceService (sorry for the long name). This interface is used by the MsmqListenerService to handle persistence of all subscriptions created at runtime to a given MSMQ Queue. This interface has three methods that are consumed by the listener service: Persist(string host, MsmqSubscription subscription): This method should take the specified subscription and save it to a persistent storage, and is called when an MsmqReceiveActivity subscribes to a given MSMQ Queue. This method is called inside a System.Transactions.TransactionScope so that the listener service can abort the persistence if anything happens after that. IEnumerable<MsmqSubscription> LoadAll(string host): This method is called when the listener service is started (right after the WorkflowEngine is started on the process, in fact) to get a list of all subscriptions stored for the given host. For each subscription that is loaded, the listener service configures again a listener on the queue the subscription relates to. Remove(MsmqSubscription subscription): This method is called when a MsmqReceiveActivity removes a subscription to a queue. It should delete any record kept about the specified subscription in the persistent storage. The host argument to Persist() and LoadAll() is a very basic mechanism to allow you to keep a single persistent storage for subscriptions coming from multiple applications (i.e. multiple processes/machines hosting the WorkflowRuntime). The host name to use is specified when you create the MsmqListenerService instance either through an argument in a new constructor overload, or through the configuration file through the “hostname” attribute. If you do not specify a hostname, the value “default” will be used instead. Be careful to always set the hostname explicitly if you’re going to be sharing the persistence storage. Out of the box, I provide two implementations of the IMsmqSubscriptionPersistenceService interface: NullMsmqSusbcriptionPersistenceService: This is an empty implementation that doesn’t do anything. It can be used if you simply don’t want or need to support subscription persistence. SqlMsmqSubscriptionPersistenceService: This implementation stores all subscriptions as records in a table in a SQL Server database called “MsmqSubscriptions”. You can select which implementation to use by simply adding it to the Read More...