Linq to XML 未得到结果

Question

我正在使用 linq to xml 创建结构列表。

linq 路径找不到概念元素。我已经尝试过各种形式，在我放弃并使用 xpath 之前，我希望有人可以向我展示 linq 方式。谢谢

xml

<response xmlns="http://www.domain.com/api">
  <about>
    <requestId>E9B73CA1F16A670C966BE2BABD3B2B22</requestId>
    <docId>09E167D994E00B0F511781C40B85AEC3</docId>
    <systemType>concept</systemType>
    <configId>odp_2007_l1_1.7k</configId>
    <contentType>text/plain</contentType>
    <contentDigest>09E167D994E00B0F511781C40B85AEC3</contentDigest>
    <requestDate>2011-10-18T09:51:28+00:00</requestDate>
    <systemVersion>2.1</systemVersion>
  </about>
  <conceptExtractor>
    <conceptExtractorResponse>
      <concepts>
        <concept weight="0.010466908" label="hell"/>
      </concepts>
    </conceptExtractorResponse>
  </conceptExtractor>
</response>

这是我所拥有的

public struct conceptweight
{
    public string concept { get; set; }
    public string weight { get; set; }
}

List<conceptweight> list = (from c
  in d.Descendants("response")
      .Descendants("conceptExtractor")
      .Descendants("conceptExtractorResponse")
      .Descendants("concepts")
  select new conceptweight()
         {
           concept = c.Attribute("label").Value,
           weight = c.Attribute("weight").Value
         }).ToList();

Answer 1

您忘记了根元素中默认的名称空间。试试这个：

// Note: names changed to follow conventions, and now a class
// rather than a struct. Mutable structs are evil.
public class ConceptWeight
{
    public string Concept { get; set; }
    // Type changed to reflect the natural data type
    public double Weight { get; set; }
}

XNamespace ns = "http://www.domain.com/api";

// No need to traverse the path all the way, unless there are other "concepts"
// elements you want to ignore. Note the use of ns here.
var list = d.Descendants(ns + "concepts")
            .Select(c => new ConceptWeight
                    {
                        Concept = (string) c.Attribute("label"),
                        Weight = (double) c.Attribute("weight"),
                    })
            .ToList();

我在这里没有使用查询表达式，因为它没有添加任何值 - 您只是执行 from x in y select z ，这可以通过 Select 更简单地表达 扩展方法。

Answer 2

XNamespace n = "http://www.domain.com/api";
List<conceptweight> list = (from c in d.Elements(n + "response").Elements(n + "conceptExtractor").Elements(n + "conceptExtractorResponse").Elements(n + "concepts").Elements(n + "concept")
                            select new conceptweight
                            {
                                concept = c.Attribute("label").Value,
                                weight = c.Attribute("weight").Value
                            }).ToList();

您忘记了命名空间和最后一个元素（concept）。啊，如果您进行内联初始化，则不需要 new ConceptWeight 中的 () 括号。 Ah 和后代将遍历元素的所有“级别”。如果您想“手动”遍历它，请使用 Elements。