private void Form1_Load(object sender, System.EventArgs e)
{
  XmlValidatingReader reader = new XmlValidatingReader( 
    new XmlTextReader( new StringReader(target) ) );
  reader.ValidationType = ValidationType.None;
  while (reader.Read())
  {
    Trace.WriteLine("ノードを発見: " + reader.NodeType.ToString());
    if( reader.NodeType == XmlNodeType.Text )
    {
      Trace.WriteLine(reader.Value);
    }
    if( reader.NodeType == XmlNodeType.EntityReference )
    {
      Trace.WriteLine(reader.Name);
    }
  }
}