Linq to XML問題

Question

鑑於以下XML，我可以使用什麼查詢將preapprovalKey的值提取到字符串變量？ LINQ to XML還有一點新意。

<?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> 

Answer 1

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