如何使用 LINQ to XML 正确从具有命名空间的 XML 文档中的'ActivityID”属性中提取 GUID？

使用 XDocuments 中的命名空间进行 LINQ to XML

使用 XDocuments 中的命名空间查询 XML 可能具有挑战性。考虑以下 XML：

<e2etraceevent xmlns="http://schemas.microsoft.com/2004/06/E2ETraceEvent">
    <system xmlns="http://schemas.microsoft.com/2004/06/windows/eventlog/system">
        <eventid>589828</eventid>
        <type>3</type>
        <subtype name="Information">0</subtype>
        <level>8</level>
        <timecreated systemtime="2010-06-01T09:45:15.8102117Z"></timecreated>
        <source name="System.ServiceModel"></source>
        <correlation activityid="{00000000-0000-0000-0000-000000000000}"></correlation>
        <execution processname="w3wp" processid="5012" threadid="5"></execution>
        <channel></channel>
        <computer>TESTSERVER3A</computer>
    </system>
    <applicationdata>
        <tracedata>
            <dataitem>
                <tracerecord xmlns="http://schemas.microsoft.com/2004/10/E2ETraceEvent/TraceRecord" severity="Information">
                    <traceidentifier>http://msdn.microsoft.com/en-GB/library/System.ServiceModel.Activation.WebHostCompilation.aspx</traceidentifier>
                    <description>Webhost compilation</description>
                    <appdomain>/LM/W3SVC/257188508/Root-1-129198591101343437</appdomain>
                    <source>System.ServiceModel.Activation.ServiceParser/39498779</source>
                    <extendeddata xmlns="http://schemas.microsoft.com/2006/08/ServiceModel/StringTraceRecord">
                        <virtualpath>/Service.svc</virtualpath>
                    </extendeddata>
                </tracerecord>
            </dataitem>
        </tracedata>
    </applicationdata>
</e2etraceevent>

以下代码不会从“ActivityID”属性中提取 GUID：

XDocument xDoc = XDocument.Parse(CurrentString);
XElement xEl1 = xDoc.Element("E2ETraceEvent");
XElement xEl2 = xEl1.Element("System");
XElement xEl3 = xEl2.Element("Correlation");
XAttribute xAtt1 = xEl3.Attribute("ActivityID");
String sValue = xAtt1.Value;

解决方案：

要使用命名空间，请使用以下命令代码：

XNamespace nsSys = "http://schemas.microsoft.com/2004/06/windows/eventlog/system";
XElement xEl2 = xDoc.Element(nsSys + "System");
XElement xEl3 = xEl2.Element(nsSys + "Correlation");
XAttribute xAtt1 = xEl3.Attribute("ActivityID");
String sValue = xAtt1.Value;

试用完整源代码：

        public static void Main()
        {
            XElement xDoc = XElement.Parse(
            @"<e2etraceevent xmlns="" http:> 
    <system xmlns="" http:> 
        <eventid>589828</eventid> 
        <type>3</type> 
        <subtype name="" information>0</subtype> 
        <level>8</level> 
        <timecreated systemtime=""></timecreated> 
        <source name="" system.servicemodel></source> 
        <correlation activityid=""></correlation> 
        <execution processname="" w3wp processid="" threadid=""></execution> 
        <channel></channel> 
        <computer>TESTSERVER3A</computer> 
    </system> 
    <applicationdata> 
        <tracedata> 
            <dataitem> 
                <tracerecord xmlns="" http: severity="" information> 
                    <traceidentifier>http://msdn.microsoft.com/en-GB/library/System.ServiceModel.Activation.WebHostCompilation.aspx</traceidentifier> 
                    <description>Webhost compilation</description> 
                    <appdomain>/LM/W3SVC/257188508/Root-1-129198591101343437</appdomain> 
                    <source>System.ServiceModel.Activation.ServiceParser/39498779</source> 
                    <extendeddata xmlns="" http:> 
                        <virtualpath>/Service.svc</virtualpath> 
                    </extendeddata> 
                </tracerecord> 
            </dataitem> 
        </tracedata> 
    </applicationdata> 
</e2etraceevent>");

            XNamespace nsSys = "http://schemas.microsoft.com/2004/06/windows/eventlog/system";
            XElement xEl2 = xDoc.Element(nsSys + "System");
            XElement xEl3 = xEl2.Element(nsSys + "Correlation");
            XAttribute xAtt1 = xEl3.Attribute("ActivityID");
            String sValue = xAtt1.Value;

            Console.WriteLine("sValue = {0}", sValue);

            Console.ReadKey();
        }

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