别人翻译的文章整理成的pdf；原文链接http://www.cnblogs.com/gyche/tag/WF%e4%bb%8e%e5%85%a5%e9%97%a8%e5%88%b0%e7%b2%be%e9%80%9a%e7%b3%bb%e5%88%97/