Windows Server AppFabric offers an Instance Control mechanism that allows issuing control commands to be executed against persisted instances. Instance Control also allows the ability to retrieve commands queued against a persisted workflow instance. This two-way communication enables a decoupled mechanism of handling, retrieving, and executing control commands against a persisted instance.
The Instance Control provider is responsible for providing access to an Instance Control object. Windows Server AppFabric provides a default implementation of the Instance Control provider called the SqlInstanceControl provider that runs on top of SqlWorkflowInstanceStore. We learned about SqlInstanceControl in our third recipe of this chapter, titled Programmatically controlling persisted workflow instances.
In this recipe, we will focus on building a custom Instance Control provider.