Like me, you may have read in various books and articles that there exists a restriction of one WorkflowRuntime instance for each App Domain. This is, in fact, not true. In an early beta release of WF such a restriction existed, and this fact has been perpetuated even though the restriction has long since been removed.

The following code sample is a simple demonstration to show that there is no problem creating multiple WorkflowRuntime instances. 

The Workflow1 class contains a code activity that writes a message to console and a delay activity that pauses for five seconds.

And the result:

Download the sample code: MultiRuntime.zip (27.55 kb)

Thanks go out to my learned colleague, Jeff Brokenshire, who brought it to my attention and pointed me to this blog post.