使用 linq 从带有 where 语句的 XElement 中选择

Question

我有一个 XElement 对象，它是从如下所示的 XML 构建的：

<Root>
  <Oppurtunities>
    <Oppurtunity>
      <Title> Account Manager</Title>
      <Company>Company name</Company>
      <Location>Boston</Location>
      <EndDate>2013-04-11</EndDate>
      <c>acce</c>
      <id>MNYN-95ZL8L</id>
      <Description>This is a detailed description...</Description>
    </Oppurtunity>

现在我需要从特定的 Oppurtunity 节点获取描述值，这意味着我想从 id 的特定位置获取描述。我需要做这样的事情：

//My XElement object is called oppurtunities
oppurtunities = new XElement((XElement)Cache["Oppurtunities"]);

string id = Request.QueryString["id"];

//I want to do something like this but of course this is not working
var description = (from job in oppurtunities
                              .Element("Oppurtunities")
                              .Element("Oppurtunity")
                              .Element("Description")
                              where job.Element("id") == id).SingleOrDefault();

Answer 1

您必须在查询中进一步移动.Element("Description")，以允许id 条件工作：

//I want to do something like this but of course this is not working
var description = (from job in oppurtunities
                              .Element("Oppurtunities")
                              .Elements("Oppurtunity")
                   where job.Element("id") == id
                   select job.Element("Description")).SingleOrDefault()

要将Element("id") 作为字符串进行比较，请使用(string)XElement 转换-即使找不到<id>，它也可以工作：

where (string)job.Element("id") == id

在这种情况下使用XElement.Value 将抛出NullReferenceException。