Professional Visual Basic® 2010 and .NET 4

Appendix C. Workflow 2008 Specifics

As discussed in Chapter 26, Windows Workflow Foundation (WF) has changed substantially in the .NET Framework 4. The models used to organize your workflows have changed, and many of the older activities do not have counterparts in the new version. This appendix discusses the version of WF supported by the .NET Framework versions 3.0 and 3.5 (i.e., Visual Basic 2005 with .NET Framework 3.0 and Visual Basic 2008). This information is retained in this edition for those users who still need to maintain existing WF solutions using these older versions. For new applications, the new model is highly recommended. Here, the older style of building workflows is called Windows Workflow Foundation 3.x (or just WF 3.x).

BUILDING WORKFLOWS

The actual workflow files in WF 3.x are XML files written in a version of XAML. This is the same XAML used to describe Windows Presentation Foundation (WPF) files. (See Chapter 17 for more details on WPF.) They describe the actions to perform within the workflow, and the relationship between those actions. You can create a workflow using only a text editor, but Visual Studio makes creating these workflows much easier. It provides a graphical designer that enables developers to visually design the workflow, creating the XAML in the background. The following code shows a section of the XAML for a workflow:

<RuleDefinitions xmlns="http://schemas.microsoft.com/winfx/2006/xaml/workflow"> <RuleDefinitions.Conditions> <RuleExpressionCondition ...