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Linq到XML-获取属性和元素

linq-to-xml xml .net c#

1

Sam · 技术社区 · 4 年前

给定这个XML,我如何获得每个outageEvent的数据,包括属性和元素?

最后,我需要将这些数据移动到数据库中,但这是第一步。

所需的结束格式是具有属性的每个outageEvent的“行” ObjectID 然后是outageEvent中的元素。

outageEvent
-------------
ObjectID
Comment
objectName
...etc.

此时不需要获取outageEvent的孙辈,如ExtensionList子代。

到目前为止,我正在使用Linq-to-XML进行查询。我可以查询并获取对象ID。另外,我可以查询得到所有的元素。试图把两者结合起来给我带来了麻烦。有一段时间没有做任何C#,所以这是99%的问题。

<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
    <soap:Header>
    </soap:Header>
    <soap:Body>
        <OutageEventChangedNotification xmlns="http://www.multispeak.org/Version_4.1_Release">
            <oEvents>
                <outageEvent objectID="2021-10-16-0002">
                    <comments>Test outage 2</comments>
                    <extensionsList>
                        <extensionsItem>
                            <extName>primaryCrew</extName>
                            <extValue>Primary Crew Name</extValue>
                            <extType>string</extType>
                        </extensionsItem>
                    </extensionsList>
                    <objectName>Outage Name</objectName>
                    <!-- more elements -->
                </outageEvent>
                <outageEvent objectID="2021-10-16-0001">
                    <comments>Test outage 1</comments>
                    <!-- more elements -->
                </outageEvent>
            </oEvents>
        </OutageEventChangedNotification>
    </soap:Body>
</soap:Envelope>

C#代码:

XElement outages = XElement.Parse(requestBody);
            XNamespace oecn = "http://www.multispeak.org/Version_4.1_Release";
//This works
            IEnumerable<string> outageIDs = from outage in outages.Descendants(oecn + "outageEvent")
                                                   select (string) outage.Attribute("objectID");

            foreach (string outageID in outageIDs)
            {
                Console.WriteLine($"IENUMERABLE: {outageID}");
            }

//This works
            IEnumerable<string> outageProperties = from outage in outages.Descendants(oecn + "outageEvent")
                                                   select (string)outage;

            foreach (string outageProperty in outageProperties)
            {
                Console.WriteLine($"IENUMERABLE: {outageProperty} \r\n");
            }

//This Doesn't
            var alloutages = from outage in outages.Descendants(oecn + "outageEvent")
                                  select new /*Error Here*/
                              {
                                  outageID = outage.Attribute("objectID").Value,
                                  comments = outage.Element("comments").Value
                              };
                                            

            foreach (var outage in alloutages)
            {
                Console.WriteLine($"OUTPUT: {outage.outageID}");
            }

输出

Hello World!
IENUMERABLE: 2021-10-16-0002
IENUMERABLE: 2021-10-16-0001
IENUMERABLE: Test outage 2primaryCrewPrimary Crew NamestringOutage Name0032.427326-99.788595TRANSFORMER1District9TRANSFORMER1TransformerA10FeederNameAssumed2015-01-01T10:00:00Z2015-01-01T10:30:00Z2015-01-01T11:00:00ZCrew1Crew21010Contractor44

IENUMERABLE: Test outage 1primaryCrewPrimary Crew NamestringOutage Name0032.427326-99.788595TRANSFORMER1District9TRANSFORMER1TransformerA10FeederNameAssumed2015-01-01T10:00:00Z2015-01-01T10:30:00Z2015-01-01T11:00:00ZCrew11010Contractor44

var=alloutages部分出现错误,突出显示“select new”块。

System.NullReferenceException
  HResult=0x80004003
  Message=Object reference not set to an instance of an object.
  Source=ParseXMLWithLinq
  StackTrace:
   at XMLParse.Program.<>c.<Main>b__0_2(XElement outage) in

System.Xml.Linq.XContainer.Element(...) returned null.

变异体的内容如下所示:

<outageEvent objectID="2021-10-16-0002" xmlns="http://www.multispeak.org/Version_4.1_Release">
  <comments>Test outage 2</comments>
  <extensionsList>
    <extensionsItem>
      <extName>primaryCrew</extName>
      <extValue>Primary Crew Name</extValue>
      <extType>string</extType>
       ...
</outageEvent>

1 回复 | 直到 4 年前

1

Evk 4 年前

异常的原因是 comments 元素内部 outageEvent 与在同一命名空间中 outageEvent ,所以在 http://www.multispeak.org/Version_4.1_Release 。因此,不要:

select new /*Error Here*/
{
    outageID = outage.Attribute("objectID").Value,
    comments = outage.Element("comments").Value
};

您需要做到:

select new /*Error Here*/
{
    outageID = outage.Attribute("objectID").Value,
    // use namespace you already have here
    comments = outage.Element(oecn + "comments").Value
};

另一种方法是按本地名称筛选元素:

select new /*Error Here*/
{
    outageID = outage.Attribute("objectID").Value,
    comments = outage.Elements().First(c => c.Name.LocalName == "comments").Value
};