In general, if you do not need the persistence and tracking features (which in my opinion are the main features), you shouldn't use Workflow Foundation.
Here are the advantages and disadvantages of Workflow Foundation I gathered from my experience:
Advantages
- Persistence: If you're going to have many long running processes (think days, weeks, months), then Workflows are great for this. Idle workflow instances are persisted to the database so it doesn't use up memory.
- Tracking: WF provides the mechanism to track each activity executed in a workflow
- *Visual Designer: I put this as a *, because I think this is really only useful for marketing purposes. As a developer, I prefer to write code rather than snapping things together visually. And when you have a non-developer making workflows, you often end up with a huge confusing mess.
Disadvantages
- Programming Model: You're really limited in programming features. Think about all the great features you have in C#, then forget about them. Simple one or two line statements in C# becomes a fairly large block activities. This is particularly a pain for input validation. Having said that, if you're really careful to keep only high-level logic in workflows, and everything else in C#, then it might not be a problem.
- Performance: Workflows use up a large amount of memory. If you're deploying a lot of workflows on a server, make sure you have tons of memory. Also be aware that workflows are much slower than normal C# code.
- Steep learning curve, hard to debug: As mentioned above. You're going to spend a lot of time figuring out how to get things to work, and figuring out the best way to do something.
- Workflow Version Incompatibility: If you deploy a workflow with persistence, and you need to make updates to the workflow, the old workflow instances are no longer compatible. Supposedly this is fixed in .NET 4.5.
- You have to use VB expressions (.NET 4.5 allows for C# expressions).
- Not flexible: If you need some special or specific functionality not provided by Workflow Foundation, prepare for a lot of pain. In some cases, it might not even be possible. Who knows until you try? There's a lot of risk here.
- WCF XAML services without interfaces: Normally with WCF services, you develop against an interface. With WCF XAML Services, you cannot ensure a WCF XAML Service has implemented everything in an interface. You don't even need to define an interface. (as far as I know...)
