I'm using c# .NET 4.8 and I'm trying to extract a value from an XML document. Here is a sample of the document I'm using:
<SOME_GROUP SomeValue="2">
<SOME_PLACEHOLDER SOMEDateTime="2022-02-10T14:50:48-08">
<SOME_DATA>
<MAIN_SOME SomeValue="2" MAINSOMEID="MAINSOME1">
<TARGET_FIELD MAINFIELDID="MAIN111" SomeID="somedata" _Value="someValue">
<_SUB_FIELD _Code="038" _Text="some other data"></_SUB_FIELD>
</TARGET_FIELD>
</MAIN_SOME>
</SOME_DATA>
</SOME_PLACEHOLDER>
</SOME_GROUP>
I want to get the _Value
from TARGET_FIELD
and store it in a variable. Right now I can do this using the method SelectNodes()
like this:
using System.Xml;
XmlDocument someXmlDocument = new XmlDocument();
someXmlDocument.LoadXml(someXmlFile);
var myValue = someXmlDocument.SelectNodes("/SOME_GROUP/SOME_PLACEHOLDER/SOME_DATA/MAIN_SOME/TARGET_FIELD")
.Cast<XmlNode>()
.Select(x => x.Attributes["_Value"].Value).ToList();
and I get my value someValue
in the first element of the list myValue
. It seems like because there is only one node I'm getting this value from I should use the SelectSingleNode()
method instead.
If I try this:
var myValue = someXmlDocument.SelectSingleNode("/SOME_GROUP/SOME_PLACEHOLDER/SOME_DATA/MAIN_SOME/TARGET_FIELD")
.Cast<XmlNode>()
.Select(x => x.Attributes["_Value"].Value);
the code runs but I don't get anything stored in myValue
as I expect.
If I leave off the ToList()
in an attempt to store the value in myValue
as just a string like this:
var myValue = someXmlDocument.SelectNodes("/SOME_GROUP/SOME_PLACEHOLDER/SOME_DATA/MAIN_SOME/TARGET_FIELD")
.Cast<XmlNode>()
.Select(x => x.Attributes["_Value"].Value);
then I get a null reference exception like this:
System.NullReferenceException: 'Object reference not set to an instance of an object.'
Sorry if this is a stupid question, I'm just getting back into c# development. Can anyone tell me what I'm doing wrong when trying to use SelectSingleNode()
or if that is even something I should be trying to use in this case?
As always, a correct, clearly explained answer will be marked as accepted and upvoted.
Thanks.
Try this...
public static void DoSelectSingleNode()
{
var xml = "<SOME_GROUP SomeValue=\"2\"><SOME_PLACEHOLDER SOMEDateTime=\"2022-02-10T14:50:48-08\"><SOME_DATA><MAIN_SOME SomeValue=\"2\" MAINSOMEID=\"MAINSOME1\"><TARGET_FIELD MAINFIELDID=\"MAIN111\" SomeID=\"somedata\" _Value=\"someValue\"><_SUB_FIELD _Code=\"038\" _Text=\"some other data\"></_SUB_FIELD></TARGET_FIELD></MAIN_SOME></SOME_DATA></SOME_PLACEHOLDER></SOME_GROUP>";
var xmlDocument = new XmlDocument();
xmlDocument.LoadXml(xml);
var value = xmlDocument.DocumentElement.SelectSingleNode("//TARGET_FIELD").Attributes["_Value"].InnerText;
Console.WriteLine(value);
}
... naturally, if there are more than one TARGET_FIELD
then you'll only pull back one.
I find this to be a good resource when it comes to using XPath for node selections... https://devhints.io/xpath
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