如何使用 LINQ-to_XML 查询搜索 XML

Question

我将分层数据存储在 XML 文件中。有多个公司，每个公司可以有多个业务线。他们在多个州开展每项业务。每个州都可以有多种费率结构。下面显示了一个伪造的示例。

例如，如何编写 LINQ to XML 查询来返回给定公司、业务线和州的所有费率结构？或者某家公司提供人寿保险的所有州。

示例：返回俄勒冈州 State Farm 地震保险的所有费率。

示例：返回 Travelers 提供人寿保险的所有州。

我知道如何深入一层，但不知道如何进一步深入。我只知道一旦得到答案我会拍拍我的头并“呃”，但现在我被困住了。

<?xml version="1.0" encoding="utf-8" ?>
<businessData>
  <company name="StateFarm" id="21">
    <lineOfBusiness name="Homeowners" id="24">
      <state name="Texas" abbreviation="TX">
        <rate structure="A"/>
        <rate structure="D"/>
        <rate structure="F"/>
      </state>
    </lineOfBusiness>
    <lineOfBusiness name="Earthquake" id="62">
      <state name="California" abbreviation="CA">
        <rate structure="A"/>
        <rate structure="B"/>
      </state>
      <state name="Oregon" abbreviation="OR">
        <rate structure="A"/>
      </state>
      <state name="Washington" abbreviation="WA">
        <rate structure="A"/>
      </state>
    </lineOfBusiness>
    <lineOfBusiness name="Fire" id="22">
      <state name="California" abbreviation="CA">
        <rate structure="A"/>
      </state>
    </lineOfBusiness>
  </company>
  <company name="Travellers" id="17">
    <lineOfBusiness name="Life" id="23">
      <state name="Florida" abbreviation="FL">
        <rate structure="A"/>
        <rate structure="C"/>
        <rate structure="D"/>
      </state>
      <state name="Alabama" abbreviation="AL">
        <rate structure="A"/>
        <rate structure="B"/>
        <rate structure="C"/>
      </state>
    </lineOfBusiness>
    <lineOfBusiness name="Homeowners" id="24">
      <state name="Alabama" abbreviation="AL">
        <rate structure="X"/>
        <rate structure="Y"/>
        <rate structure="X"/>
      </state>
      <state name="Arkansas" abbreviation="AR">
        <rate structure="C"/>
      </state>
      <state name="California" abbreviation="CA">
        <rate structure="G"/>
      </state>
      <state name="Florida" abbreviation="FL">
        <rate structure="D"/>
      </state>
      <state name="Georgia" abbreviation="GA">
        <rate structure="D"/>
      </state>
      <state name="Louisiana" abbreviation="LA">
        <rate structure="B"/>
      </state>
      <state name="Missouri" abbreviation="MO">
        <rate structure="A"/>
      </state>
    </lineOfBusiness>
    <lineOfBusiness name="Auto" id="25">
      <state name="California" abbreviation="CA">
        <rate structure="T"/>
        <rate structure="Y"/>
        <rate structure="Z"/>
      </state>
    </lineOfBusiness>
  </company>
  <company name="NationWide" id="79">
    <lineOfBusiness name="Earthquake" code="EQ" id="62">
      <state name="California" abbreviation="CA">
        <rate structure="B"/>
        <rate structure="C"/>
        <rate structure="D"/>
        <rate structure="G"/>
      </state>
    </lineOfBusiness>
  </company>
</businessData>

Answer 1

示例：返回俄勒冈州 State Farm 地震保险的所有费率：

var result = from company in XDocument.Load("test.xml").Root.Elements("company")
             from lineOfBusiness in company.Elements("lineOfBusiness")
             from state in lineOfBusiness.Elements("state")
             where company.Attributes("name").First().Value == "StateFarm" && 
                   lineOfBusiness.Attributes("name").First().Value == "Earthquake" &&
                   state.Attributes("name").First().Value == "Oregon"
             select state.Elements("rate");

示例：返回 Travelers 提供人寿保险的所有州：

var result = from company in XDocument.Load("test.xml").Root.Elements("company")
             from lineOfBusiness in company.Elements("lineOfBusiness")
             from state in lineOfBusiness.Elements("state")
             where company.Attributes("name").First().Value == "Travellers" &&
                   lineOfBusiness.Attributes("name").First().Value == "Life"
             select state.Attributes("name").First().Value;

当然，这假设 XML 文档针对 XSD 架构作为名称的有效性 > 属性应该存在。