What is the best approach to versioning the tracked data within workflows ?

Question

This is a general question concerning the Workflow Foundation (.NET 3.5) and versioning the data that it works with. We have a lot of custom activities that work with some data and this data may be interesting also for the future analysis of the already completed workflows (provided that we configure the tracking in such a way that it stores it in a serialized form).

It may be necessary to show the data from the past in the UI, but the data inevitably changes the structure (class definition / internal structure if it's dynamic) and the redeployed version of our library will contain the new data definition while the serialized data in the tracking database will be still in the old structure.

Is it better to use dynamic structures that don't change from the beginning (like a property bag) or rather later deal with the redeployment and somehow transform the serialized BLOB into the new one ? Have you ever used some approach in a similar scenario ?

Answer 1

A lot depends on how you deploy your application. If you use a strong name and deploy to the GAC or multiple private assembly paths deserializing a workflow will deserialize the exact version of your class. That means that you code must be able to work with multiple versions and that can be a bit of a pain. Storing data in a property bag is not going to help you there. If you use assembly redirects to point to the current version of an activity solves that part and I suppose using a property bag would make life simpler then. That said I tend to stick with dependency properties and regular serializable classes so far.

I did a series of blog posts about long running workflows and versioning where you run into exactly the same problem. Check here for more details.