Microsoft® Windows® Workflow Foundation Step by Step

Building a Workflow Runtime Factory

I mentioned this previously in the chapter, but it is important enough to mention again—there can be only a single instance of WorkflowRuntime per AppDomain. And because the majority of .NET applications use only a single AppDomain, it necessarily follows that you can generally use only a single instance of WorkflowRuntime in your application.

Whenever I hear "use only a single instance," I naturally think of using a combination of the singleton and factory patterns. The singleton pattern, if you’re unfamiliar with patterns, is simply a mechanism for assuring that no matter how many times your application requests instances of the singleton object, only one instance of the singleton is ever given out. This is ...