We already discussed about Persistence and Extensions in workflow foundation 4.0. Persistence is the way of storing the current state of a workflow into an instance store. Extensions are special classes for sharing data among child activities, workflow and Host application. In case of normal Extension, the data shared using the Extension won’t be stored to the instance store as part of the Persistence.  In real business scenario, we may need to store the Extension data as part of the workflow state. For this purpose, workflow foundation 4.0 is providing a special kind of Extension. For more details on PersistenceParticipant, please refer http://www.dotnetfunda.com/articles/article1120-workflow-foundation-40–persistenceparticipant-.aspx