aspnet 操作xml,该如何解决

aspnet 操作xml
rr.config

<?xml version="1.0" encoding="utf-8"?>
<urlrewritingnet rewriteOnlyVirtualUrls="true" contextItemsPrefix="QueryString" defaultPage="index.aspx" defaultProvider="RegEx" xmlns="http://www.urlrewriting.net/schemas/config/2006/07">
  <rewrites>
  <add name="content" virtualUrl="^http\://(.*)/(.*)-(\d+).aspx" rewriteUrlParameter="ExcludeFromClientQueryString" destinationUrl="~/Default.aspx?templet=$2&amp;id=$3&amp;page=$3" rewrite="Domain" ignoreCase="true" />
  </rewrites>
</urlrewritingnet>


  string xmlfile = Server.MapPath("~/Config/rr.config");
  XmlDocument xmlDoc = new XmlDocument();
  xmlDoc.Load(xmlfile); //加载文件 

  XmlNode xmldocSelect = xmlDoc.SelectSingleNode("rewrites"); 

为什么 xmldocSelect 是null 就是无法读出节点

------解决方案--------------------------------------------------------
是namespace的问题．
 XmlNamespaceManager xnm = new XmlNamespaceManager(xmlDoc.NameTable);
xnm.AddNamespace("xx","http://www.urlrewriting.net/schemas/config/2006/07");
XmlNode xmldocSelect = xmlDoc.SelectSingleNode("//xx:rewrites",xnm);
 

------解决方案--------------------------------------------------------
//直接找目标节点．可以跳过中间节点．


/开头是指从根节点开始找，但要写完整的路径．