C# Linq to XML查询，根据附加条件选择特定子元素

下面是我当前的LINQ查询和示例XML。我要做的是从email addresses元素中选择主电子邮件地址到User.email属性中

• 下的类型元素 如果为true，则电子邮件地址元素设置为primary
• 可能有 下有多个元素 电子邮件地址，但只有一个将被标记为主

这里最简单的方法是什么

当前Linq查询（User.Email当前为空）：

XML示例：

<?xml version="1.0" encoding="UTF-8"?>
<response>
  <response>
    <contact>
      <phone-numbers/>
      <im>
        <provider></provider>
        <username></username>
      </im>
      <email-addresses>
        <email-address>
          <type>primary</type>
          <address>alice@domain.com</address>
        </email-address>
      </email-addresses>
    </contact>
    <job-title>Account Manager</job-title>
    <type>user</type>
    <expertise nil="true"></expertise>
    <summary nil="true"></summary>
    <kids-names nil="true"></kids-names>
    <location nil="true"></location>
    <guid nil="true"></guid>
    <timezone>Eastern Time (US &amp; Canada)</timezone>
    <network-name>Domain</network-name>
    <full-name>Alice</full-name>
    <network-id>79629</network-id>
    <stats>
      <followers>2</followers>
      <updates>4</updates>
      <following>3</following>
    </stats>
    <mugshot-url>
      https://assets3.yammer.com/images/no_photo_small.gif</mugshot-url>
      <previous-companies/>
      <birth-date></birth-date>
      <name>alice</name>
      <web-url>https://www.yammer.com/domain.com/users/alice</web-url>
      <interests nil="true"></interests>
      <state>active</state>
      <external-urls/>
      <url>https://www.yammer.com/api/v1/users/1089943</url>
      <network-domains>
        <network-domain>domain.com</network-domain>
      </network-domains>
      <id>1089943</id>
      <schools/>
      <hire-date nil="true"></hire-date>
      <significant-other nil="true"></significant-other>
    </response>
  <response>
    <contact>
      <phone-numbers/>
      <im>
        <provider></provider>
        <username></username>
      </im>
      <email-addresses>
        <email-address>
          <type>primary</type>
          <address>bill@domain.com</address>
        </email-address>
      </email-addresses>
    </contact>
    <job-title>Office Manager</job-title>
    <type>user</type>
    <expertise nil="true"></expertise>
    <summary nil="true"></summary>
    <kids-names nil="true"></kids-names>
    <location nil="true"></location>
    <guid nil="true"></guid>
    <timezone>Eastern Time (US &amp; Canada)</timezone>
    <network-name>Domain</network-name>
    <full-name>Bill</full-name>
    <network-id>79629</network-id>
    <stats>
      <followers>3</followers>
      <updates>1</updates>
      <following>1</following>
    </stats>
    <mugshot-url>
      https://assets3.yammer.com/images/no_photo_small.gif</mugshot-url>
      <previous-companies/>
      <birth-date></birth-date>
      <name>bill</name>
      <web-url>https://www.yammer.com/domain.com/users/bill</web-url>
      <interests nil="true"></interests>
      <state>active</state>
      <external-urls/>
      <url>https://www.yammer.com/api/v1/users/1089920</url>
      <network-domains>
        <network-domain>domain.com</network-domain>
      </network-domains>
      <id>1089920</id>
      <schools/>
      <hire-date nil="true"></hire-date>
      <significant-other nil="true"></significant-other>
    </response>
</response>

主要的，重要的
alice@domain.com
客户经理
用户
东部时间（美国和加拿大）
领域
爱丽丝
79629
2.
4.
3.
https://assets3.yammer.com/images/no_photo_small.gif
爱丽丝
https://www.yammer.com/domain.com/users/alice
积极的
https://www.yammer.com/api/v1/users/1089943
domain.com
1089943
主要的，重要的
bill@domain.com
办公室经理
用户
东部时间（美国和加拿大）
领域
比尔
79629
3.
1.
1.
https://assets3.yammer.com/images/no_photo_small.gif
账单
https://www.yammer.com/domain.com/users/bill
积极的
https://www.yammer.com/api/v1/users/1089920
domain.com
1089920

像这样：

response.Descendants("email-address")
        .Single(a => a.Element("type").Value == "primary")
        .Element("address").Value

请注意，如果没有一个匹配的元素，这将引发异常。
如果不需要，请调用

FirstOrDefault

---

您可能希望使用Lambda表达式将

.Element（“联系人”）.Element（“电子邮件地址”）.Element（“电子邮件地址”）

替换为

.Element（“电子邮件地址”）
：

var users = xdoc.Root.Elements( "response" )
    .Where( x => !string.IsNullOrEmpty( x.Element( "id" ).Value ) )
    .Select( x => new User
              {
                Id = x.Element( "id" ).Value,
                Name = x.Element( "full-name" ).Value,
                Email = x.Descendants( "email-address" )
                            .Where( y => y.Element( "type" ).Value == "primary" )
                            .First().Element( "address" ).Value,
                JobTitle = x.Element( "job-title" ).Value,
                NetworkId = x.Element( "network-id" ).Value,
                Type = x.Element( "type" ).Value,
              } );

查询表达式没有太大不同：

var users = from response in xdoc.Descendants( "response" )
            where response.Element( "id" ) != null
            select new User
            {
                Id = response.Element( "id" ).Value,
                Name = response.Element( "full-name" ).Value,
                Email = response.Descendants( "email-address" )
                            .Where( x => x.Element( "type" ).Value == "primary" )
                            .First().Element( "address" ).Value,
                JobTitle = response.Element( "job-title" ).Value,
                NetworkId = response.Element( "network-id" ).Value,
                Type = response.Element( "type" ).Value
            };

是否总有一个元素的primary设置为true？是。始终有一个主元素设置为true。我不喜欢这种XML格式，我无法控制它；）感谢@Metro Surf的回答。它帮助解决了我的一个问题。
var users = from response in xdoc.Descendants( "response" )
            where response.Element( "id" ) != null
            select new User
            {
                Id = response.Element( "id" ).Value,
                Name = response.Element( "full-name" ).Value,
                Email = response.Descendants( "email-address" )
                            .Where( x => x.Element( "type" ).Value == "primary" )
                            .First().Element( "address" ).Value,
                JobTitle = response.Element( "job-title" ).Value,
                NetworkId = response.Element( "network-id" ).Value,
                Type = response.Element( "type" ).Value
            };