http://blog.csdn.net/testcs_dn/article/details/8726480
http://www.myexception.cn/asp-dotnet/1341569.html
http://blog.sina.com.cn/s/blog_8100033e0101kcfj.html
http://www.cnblogs.com/hfzsjz/archive/2010/01/19/1651216.html
http://blog.csdn.net/hsg77/article/details/6709275