Microsoft® Windows® Workflow Foundation Step by Step

The CorrelationParameter Attribute

If you think about situations where a single host application might orchestrate multiple workflow instances, you will probably find that methods and events that pass data also pass some sort of unique identifier. An order processing system might pass a customer ID, or a packaging system might pass a lot number. This type of unique identifier is a perfect candidate for identifying unique instances of data, and in fact, that’s precisely what happens.

When you design the methods and events in your communication interface, you design into their signatures a data correlation ID. The data correlation ID doesn’t have to be unique for all space and time, like a Guid. However, if it isn’t a Guid, it must be used uniquely ...