Linq To XML:在结点下查询某一类型结点

XElement firstParticipant; 
 
//  A full document with all the bells and whistles. 
XDocument xDocument = new XDocument( 
  new XDeclaration("1.0", "UTF-8", "yes"), 
  new XDocumentType("BookParticipants", null, "BookParticipants.dtd", null), 
  new XProcessingInstruction("BookCataloger", "out-of-print"), 
  //  Notice on the next line that we are saving off a reference to the first 
  //  BookParticipant element. 
  new XElement("BookParticipants", firstParticipant = 
    new XElement("BookParticipant", 
      new XComment("This is a new author."), 
      new XProcessingInstruction("AuthorHandler", "new"), 
      new XAttribute("type", "Author"), 
      new XElement("FirstName", "Joe"), 
      new XElement("LastName", "Rattz")), 
    new XElement("BookParticipant", 
      new XAttribute("type", "Editor"), 
      new XElement("FirstName", "Ewan"), 
      new XElement("LastName", "Buckingham")))); 
 
foreach (XNode node in firstParticipant.Nodes().OfType<XElement>()) 
{ 
  Console.WriteLine(node); 
}

<FirstName>Joe</FirstName> 
<LastName>Rattz</LastName>