c# - 通过 linq to xml 选择属性值

Question

在我的 xml 文件中，我如何通过 linq to xml 选择 ServiceAssignment 元素中属性 TagId 的值

注意:此 xml 在字符串属性中，不在 xml 文件中

<AnchoredXml xmlns="urn:schema:Microsoft.Rtc.Management.ScopeFramework.2008" SchemaWriteVersion="1">
  <Key ScopeClass="Global">
    <SchemaId Namespace="urn:schema:Microsoft.Rtc.Management.Settings.ServiceAssignment.2008" ElementName="ServiceAssignments" />
    <AuthorityId Class="Host" InstanceId="00000000-0000-0000-0000-000000000000" />
  </Key>
  <Dictionary Count="1">
    <Item>
      <Key />
      <Value Signature="2ffb6b0d-0239-4016-b08b-40520d1687ff">
        <ServiceAssignments xmlns="urn:schema:Microsoft.Rtc.Management.Settings.ServiceAssignment.2008">
          <ServiceAssignment TagId="659550892">
            <Component Name="Registrar">
              <ServiceId xmlns="urn:schema:Microsoft.Rtc.Management.Deploy.Topology.2008" SiteId="1" RoleName="Registrar" Instance="1" />
            </Component>
            <Component Name="PresenceFocus">
              <ServiceId xmlns="urn:schema:Microsoft.Rtc.Management.Deploy.Topology.2008" SiteId="1" RoleName="UserServices" Instance="1" />
            </Component>
          </ServiceAssignment>
          <ServiceAssignment TagId="911048693">
            <Component Name="Registrar">
              <ServiceId xmlns="urn:schema:Microsoft.Rtc.Management.Deploy.Topology.2008" SiteId="1" RoleName="Registrar" Instance="2" />
            </Component>
            <Component Name="PresenceFocus">
              <ServiceId xmlns="urn:schema:Microsoft.Rtc.Management.Deploy.Topology.2008" SiteId="1" RoleName="UserServices" Instance="2" />
            </Component>
          </ServiceAssignment>
        </ServiceAssignments>
      </Value>
    </Item>
  </Dictionary>
</AnchoredXml>

我尝试了这段代码，但给我一个空异常

var MyList = doc.Root.Elements("ServiceAssignment").Select(c=>c.Attribute(("TagId")).Value).ToList();

Answer 1

文档中有命名空间元素，因此需要将它们包含在查询中。

XNamespace itemNs = "urn:schema:Microsoft.Rtc.Management.ScopeFramework.2008";
XNamespace assignmentNs = "urn:schema:Microsoft.Rtc.Management.Settings.ServiceAssignment.2008";
var query =
    from item in doc.Descendants(itemNs + "Item")
    from assignment in item.Descendants(assignmentNs + "ServiceAssignment")
    select (long)assignment.Attribute("TagId");