private void Form1_Load(object sender, System.EventArgs e)
{
  XmlDocument doc = new XmlDocument();
  doc.Load(@"c:\sample.xml");
  XmlNodeList list = doc.GetElementsByTagName("名前");
  foreach( XmlNode node in list )
  {
    if( node.ParentNode.NodeType == XmlNodeType.Element
      && node.ParentNode.Name == "著者" )
    {
      Trace.WriteLine(node.InnerText);
    }
  }
}