参考链接：
http://blog.csdn.net/jjx0224/article/details/6164128
http://blog.csdn.net/wangzl1163/article/details/71195072
https://www.cnblogs.com/KeithWang/archive/2012/02/22/2363443.html
https://www.cnblogs.com/Johnny_Z/archive/2012/06/23/2559408.html
https://www.cnblogs.com/yukaizhao/archive/2011/07/22/xml-serialization.html
https://www.cnblogs.com/yukaizhao/archive/2011/07/19/csharp_xmldocument_access_xml.html