学步园

SelectNodes("//root/path");
SelectSingleNode("descendant::ContributingSubdomains");  
SelectNodes("//book[@genre='novel2'   and   @publicationdate='1992']"))  
SelectNodes("descendant::book[author/first-name='Margaret'and   author/last-name='Atwood']");  

前面加"@"就是属性了，不加就是节点