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[英]How to know using deserialized object if any particular node in xml exists
[英]How to check if a particular XML node exists by using LINQ
由于"<dnsServer>"
或"<dnsServers>"
标签不存在,因此出现错误。 我正在尝试检查它是否为空,但是我的代码无法正常工作。 我得到错误:
{“你调用的对象是空的。”}
这是代码:
var networkElement = doc.Root
.Element("networkAdapters")
.Elements("networkAdapter")
.First(a => (string)a.Attribute("id") == networkAdapter.networkAdapterId.ToString());
var dnsServers = networkElement.Element("dnsServers")
.Elements("dnsServer") == null ? null : networkElement.Element("dnsServers").Elements("dnsServer");
和XML示例:
<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<server id="454a8a22-8e9e-4023-9a8e-c8a4e0f259b3" productName="Manifest" created="2014-01-16T22:07:28" name="SERVER001">
<networkAdapters>
<networkAdapter id="bfcbda99-719c-4b0c-b7b2-b9167350c982" busLocation="0-N2" permanentMacAddress="00144FE5448E" physicalAdapter="True" ipEnabled="False">
<defaultGateways />
<ipAddresses />
</networkAdapter>
<networkAdapter id="73606723-fd91-40df-96dd-0bff7851cea6" ipEnabled="True">
<defaultGateways>
<defaultGateway address="99.15.210.1" index="0" />
</defaultGateways>
<ipAddresses>
<ipAddress address="99.15.210.7" subnetMask="255.255.255.224" index="0" />
</ipAddresses>
</networkAdapter>
<networkAdapter id="6520a041-2cf3-40b1-b123-1eb13f704442" busLocation="0-N3" permanentMacAddress="00144FE5448F" physicalAdapter="True" ipEnabled="False">
<defaultGateways />
<ipAddresses />
</networkAdapter>
</networkAdapters>
</server>
谢谢
请尝试以下操作:
var servers = networkElement.Element("dnsServers") ?? new XElement("dnsServers");
var dnsServers = servers.Elements("dnsServer");
当文档中没有任何内容时,它将创建空的<dnsServers>
,以使Elements("dnsServer")
查询无例外地工作。
您可以单线执行此操作:
var dnsServers = (networkElement.Element("dnsServers") ?? new XElement("dnsServers")).Elements("dnsServer");
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