Chapter 2. WF Programs

In chapter 1, "deconstructing WF," we introduced a new way of writing reactive programs. The basis of this approach is a bookmarking substrate upon which we developed a CLR type representing a reusable program statement. We also established the need for a small but specialized runtime environment that manages the execution of programs that are composed of these resumable program statements.

In WF, a resumable program statement is called an activity. A resumable program is a composition of activities. In WF, such a program is often called a workflow, but we favor the precision of the term WF program in this book because "workflow" is used colloquially. The execution environment for WF programs is called the WF runtime.

The ideas presented in Chapter 1 are the heart and soul of the WF programming model. But to actually write and run a WF program, we need to roll up our sleeves and start to use the types in the System.Workflow namespace that bring the ideas of bookmarking and continuationspresented in Chapter 1 in raw formto fruition within a fully developed programming model. The goal of this chapter is to cover the basics: We will write several activities and then run WF programs that use those activities. Later chapters will explore, in great detail, the rich set of features that surround WF's core bookmarking capabilities, which constitute the foundation of the WF programming model.