Critical Changes from WF 4.0 Beta 1 to Beta 2

There are very important changes between the two beta versions as was just published by the WF and WCF team blog.

I would like to summarize the most critical updates. (There more changes I will describe in future posts)

1. The activity class hierarchy changed dramatically.

From :

To:

• WorkflowElement goes away, and is replaced with Activity.  Activity is the root type for all units of execution within the world of WF
• Addition of ActivityWithResult which is the base for the Expression activities
• Addition of AsyncCodeActivity.  We got a lot of feedback that people liked what we were doing integrating asynchronous programming within activities but that there was still a fair amount of work in order to hook those up.  AsyncCodeActivity is some nice sugar that makes it pretty easy to write an activity that takes advantage APIs that surface a Begin/End pair using the asynchronous programming model.

2. WorkflowInstance was renamed to WorkflowApplication

3. Correlation

• XPath can now be generated from ParametersContent
• CorrelationQuery and AdditionalCorrelations have been merged into a collection called CorrelationInitializers.   Also, we’ve reduced the need for CorrelationHandles all over the place by improving the CorrelationScope and having an implicit correlation handle.

4. Parameters support : The Parameters activities were removed and merged into the Send and Receive activities.  You can now use the Content property to support MessageContent (primarily for untyped Message or MessageContract ) and ParametersContent (which is for the more RPC style list of name value pairs).

Enjoy.