搜了半天, 终于找到了它了下落:
MSDN摘抄:
State machine functionality in Windows Workflow Foundation (WF) was introduced as part of the Microsoft .NET Framework 4 Platform Update 1 (KB2478063). To create state machine workflow applications in Visual Studio 2010, the Microsoft .NET Framework 4 Platform Update 1 – Design-time Package for Visual Studio 2010 SP1 (KB2495593) is required. For more information and instructions on how to download and configure these updates, click here.
总结得出下面的结论:
1.VS2010里没有State Machine, 只有Sequence和FlowChart两种工作流, State Machine没有随VS2010发布.
2.WF4 State Machine已经结束CTP, 现在已经正式发布了, 存在.NET Framework 4 Platform Update 1中, 如果要装.NET Framework 4 Platform Update 1, 您得先装VS 2010 SP1, 大约1.4G, 可能仅能在线安装.
3.State Machine在.Net 4.5中被正式的包含了进去.
推荐资料:
.NET Framework 4 Platform Update 1 State Machine Workflows
http://msdn.microsoft.com/en-us/library/ee264171(v=VS.100).aspx
State Machine Workflows
http://msdn.microsoft.com/en-us/library/ee264171(v=VS.110).aspx
参考：http://blogs.msdn.com/b/endpoint/archive/2011/04/18/microsoft-net-framework-4-platform-update-1.aspx