Windows Workflow Foundation (WF) provides the programming model, engine and tools for quickly building workflow-enabled applications on Windows. It comprises a new .NET Framework namespace called System.Workflow, an in-process workflow engine and workflow designers for Visual Studio 2005 and Visual Studio 2008 ("Orcas"). WF provides full support for Visual Basic.NET and C#, debugging and a graphical workflow designer. You can develop your workflow completely in code or as declarative XML (XAML). It provides an extensible model and designer to build custom activities that encapsulate workflow functionality for end users or for reuse across multiple projects. It runs on both Windows clients (XP and Vista) and Windows Servers (2003 and 2008).