Linq to XML Question

问题

Given the following XML, what query can I use to extract the value of preapprovalKey to a string variable? Still a little new to LINQ to XML.

  <?xml version="1.0" encoding="UTF-8" ?> 
- <ns2:PreapprovalResponse xmlns:ns2="http://svcs.paypal.com/types/ap">
- <responseEnvelope>
  <timestamp>2011-04-05T18:35:32.952-07:00</timestamp> 
  <ack>Success</ack> 
  <correlationId>7cec030fa3eb2</correlationId> 
  <build>1655692</build> 
  </responseEnvelope>
  <preapprovalKey>PA-9AG427954Y7578617</preapprovalKey> 
  </ns2:PreapprovalResponse>

回答1:

XDocument doc = XDocument.Load("test.xml");
string preapprovalKey = doc.Descendants("preapprovalKey").Single().Value;

来源：https://stackoverflow.com/questions/5560697/linq-to-xml-question