XML 네임스페이스(XML Namespaces)에 대한 자세한 설명과 노드 읽기 방법에 대한 샘플 코드

   <name>African Coffee Table</name>
   <width>80</width>
   <length>120</length>

（转原文http://www.cnblogs.com/mgen/archive/2011/05/24/2056025.html）

<a xmlns="mgen.cnblogs.com">
    <b>ccc</b>
</a>

If the XPath expression does not include a prefix, it is assumed that the namespace URI is the empty namespace. 
If your XML includes a default namespace, you must still add a prefix and namespace URI to the XmlNamespaceManager; 
otherwise, you will not get any nodes selected

<?xmlversion="1.0" encoding="utf-8"?>
<rootxmlns="dotnet" xmlns:w="wpf">
  <a>data in a</a>                
  <w:b>data in b</w:b>         
  <cxmlns="silverlight">
    <w:d>                             
      <e>data in e</e>              
    </w:d>
  </c>
</root>

<?xmlversion="1.0" encoding="utf-8"?>
<rootxmlns="dotnet" xmlns:w="wpf">
  <!-- xmlns: dotnet -->
  <a>data in a</a>
  <!-- xmlns: dotnet -->
  <w:b>data in b</w:b>
  <!-- xmlns: wpf -->
  <cxmlns="silverlight">
    <!-- xmlns: silverlight -->
    <w:d>
      <!-- xmlns: wpf -->
      <e>data in e</e>
      <!-- xmlns: silverlight -->
    </w:d>
  </c>
</root>

   /*
              * 假设上面XML文件在C:\a.txt中
              * 下面代码会查询目标节点e，并输出数据：data in e
              * */
 
            var xmlDoc =newXmlDocument();
            xmlDoc.Load(@"C:\a.txt");
 
            //加入命名空间和前缀
            var xmlnsm =newXmlNamespaceManager(xmlDoc.NameTable);
            xmlnsm.AddNamespace("d", "dotnet");
            xmlnsm.AddNamespace("s", "silverlight");
            xmlnsm.AddNamespace("w", "wpf");
 
            var node = xmlDoc.SelectSingleNode("/d:root/s:c/w:d/s:e", xmlnsm);
            Console.WriteLine(node.InnerText);
 
            //输出：data in e