C# - Linq - XPathSelectElement 每次都返回相同的结果

Question

我在读取一些 xml 行时遇到了 XPathSelectElement 的问题....

函数 handleEachSession 从我的其他函数的 mathod childList.ForEach() 调用了两次:

private void handleMonitorResponse(XElement receivedSessions)
 {
 List<XElement> childList = receivedSessions.Elements().ToList();
 childList.ForEach(handleEachSession);

childList 有两个元素(两行 XML 行，我希望它有)然后我可以在调试器中看到 handleEachSession() 的两次调用都获得了正确的 XElement session 。我希望它有这两个。

现在有这些 XPathSelectElement 的。它适用于第一次通话，但不适用于第二次通话。我第二次获得新的 XElement session ，但 XPathSelectElement 仍然返回第一次调用的旧值。哼!？？我无法理解这种行为。

private void handleEachSession(XElement session)
 {
 XElement receivedSessionId = session.XPathSelectElement("//sessionId");
 XElement receivedQuality = session.XPathSelectElement("//quality");
 XElement receivedContentStatus = session.XPathSelectElement("//contentStatus");
…

谁能帮帮我？

XML 是:

receivedSessions = 
<sessions type="array">
  <item type="object">
    <sessionId type="string">8c86716a87</sessionId>
    <quality type="string">mid</quality>
    <addressUri type="string">http://192.168.6.234/media/SorrowPinkFloyd_.mp4</addressUri>
    <currentTime type="number">1.5542887</currentTime>
    <contentStatus type="string">paused</contentStatus>
  </item>
  <item type="object">
    <sessionId type="string">c795067c4e</sessionId>
    <quality type="string">mid</quality>
    <addressUri type="string">http://192.168.6.234/media/trailer.mp4</addressUri>
    <currentTime type="number">3.3492105</currentTime>
    <contentStatus type="string">playing</contentStatus>
  </item>
</sessions>

session = (first call)
<item type="object">
  <sessionId type="string">8c86716a87</sessionId>
  <quality type="string">mid</quality>
  <addressUri type="string">http://192.168.6.234/media/SorrowPinkFloyd_.mp4</addressUri>
  <currentTime type="number">1.5542887</currentTime>
  <contentStatus type="string">paused</contentStatus>
</item>

session = (second call)
<item type="object">
  <sessionId type="string">c795067c4e</sessionId>
  <quality type="string">mid</quality>
  <addressUri type="string">http://192.168.6.234/media/trailer.mp4</addressUri>
  <currentTime type="number">3.3492105</currentTime>
  <contentStatus type="string">playing</contentStatus>
</item>

Answer 1

根据xpath-syntax ，双斜杠 (//) 表示:从当前节点中选择文档中与选择匹配的节点，无论它们位于何处。所以考虑到这一点，您可能必须将 handleEachSession 函数更改为

private void handleEachSession(XElement session)
{
    XElement receivedSessionId = session.XPathSelectElement("sessionId");
    XElement receivedQuality = session.XPathSelectElement("quality");
    XElement receivedContentStatus = session.XPathSelectElement("contentStatus");
}