The Flow is the center of workflow itself, and how to control the Flow is what we will see in this chapter. WF is a lot like an imperative programming language such as C# when it comes to flow control; we have many similar concepts in WF4 such as "if-else", "foreach", "switch", "try-catch", and so on. Additionally, there are some other flow control activities that enable us to control workflow easily and efficiently such as the Parallel activity, Pick activity, ParallelForEach<T> activity, and so on.
In C#, we use language control key words to control everything. In WF4, this is slightly different. When we are developing a real workflow application, we will still write business logic in .NET code and build it out as DLL files so that we can reuse it everywhere. WF4 has two different types of workflow—Sequence workflow and Flowchart workflow. The famous State Machine workflow will be released in .NET Framework 4.5.