https://blog.csdn.net/zhoufoxcn/article/details/2220533
http://www.cnblogs.com/wangsaiming/archive/2013/01/11/2856253.html
https://blog.csdn.net/giraffe_zj/article/details/3343184配置详解
http://logging.apache.org/log4net/release/sdk/html/帮助文档
下载log4net + 配置文件