SCSF – Loading modules into child WorkItems

The Composite UI Application Block (CAB) used in the Smart Client Software Factory (SCSF) allows you to specify which modules will be loaded using an XML file or a web service. The problem is that all the modules you specify get loaded into the root WorkItem. If you have a services module, for example, that is used only by one WorkItem, you have to choose between loading it in the root WorkItem and explicitly loading it in the “AddServices” method of your WorkItemController.

The first option can generate EventBroker problems – all events published by the service will be visible to all WorkItems and vice versa, so you might get some “surprise” event calls.

In the second option you get a tight coupling between the module and its services (not always a real problem, but if you have the service in a separate assembly it could be because you are trying to isolate change between them).

The solution we want is to use the same mechanism as the root WorkItem and load the modules defined in an XML file. One way to do this is to create a service that will be available to child WorkItems.

Message Contracts in WCF and the Smart Client Software Factory

We’re developing a new product and we took the chance to change from ASMX web services to WCF. We’re using the Service Software Factory and the Smart Client Software Factory from patterns & practices. I have to admit we’re not experts in WCF yet, but the best way to learn is to practice.

The Service Factory makes it easy to declare Data Contracts (there is even an option to decorate an existing class), Message Contracts and Service Contracts. Basically, a Service Contract defines one or more Operation Contracts that use the Data Contracts as parameters.

So where do the Message Contracts come into play? The Service Software Factory Help says:

“A message contract is a class that represents a request or response message. While data contracts represent types that are reused across services and operations within a service, message contracts are defined for a specific operation on a service and are not reused.”

This and the example that follows on how to define the Message Contracts led us to think about the Message Contracts more as wrappers for the request and response for an operation.