I am writing a c# code which requires me to parse an xml file. The statement that i need is
XmlDocument xmlt = new XmlDocument();
xmlt.Load(XMLFile1.xml");
XmlNode node = xmlt.SelectSingleNode("//abc/data[#name='xyz']/value");
where abc is the root node.
I am searching the data attribute #name to match with xyz, what should i do if instead of hard coding xyz i need a variable, say name_var. I basically need a code which performs the function so that i cn put #name=name_var instead of xyz.
name_var is varied in the c# code
As far as I know the SelectNodes and SelectSingleNode methods do not provide an overload to provide some variable resolution so all you can do is construct a string e.g.
string name = "xyx";
XmlNode node = xmlt.SelectSingleNode(string.Format("abc/data[#name = '{0}']/value", name));
Of course that approach breaks as soon as the name value contains a single quote ' character. If you need variable resolution in XPath then look into XPathNavigator, it allows that with some effort: http://msdn.microsoft.com/en-us/library/vstudio/dd567715%28v=vs.100%29.aspx.
Related
I'm trying to get values from a XML document using the iXF format, but I'm having some issues with the XPath syntax.
I have the following XML document
<SOAP_ENV:Envelope xmlns:NS2="http://www.ixfstd.org/std/ns/core/classBehaviors/links/1.0" xmlns:NS1="CATIA/V5/Electrical/1.0" xmlns:tns="IXF_Schema.xsd" xmlns:ixf="http://www.ixfstd.org/std/ns/core/1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:SOAP_ENV="http://schemas.xmlsoap.org/soap/envelope/" xsi:schemaLocation="IXF_Schema.xsd ElectricalSchema.xsd">
<SOAP_ENV:Body>
<ixf:object id="Electrical Physical System00000089.1" xsi:type="tns:Harness">
<tns:Name>Electrical Physical System00000089.1</tns:Name>
</ixf:object>
<ixf:object id="X10(1)//X11(1)" xsi:type="tns:Wire">
<tns:Name>X10(1)//X11(1)</tns:Name>
<NS1:Wire>
<NS1:Length>763,752mm</NS1:Length>
<NS1:Color>RD</NS1:Color>
<NS1:OuterDiameter>1,32mm</NS1:OuterDiameter>
</NS1:Wire>
</ixf:object>
</SOAP_ENV:Body>
</SOAP_ENV:Envelope>
And i'm trying to find all the Wire objects and get the Name and Length values with the following code.
XmlDocument xlDocument = new XmlDocument();
xlDocument.Load(importFile);
XmlNamespaceManager nsManager = new XmlNamespaceManager(xlDocument.NameTable);
nsManager.AddNamespace("tns", "IXF_Schema.xsd");
nsManager.AddNamespace("xsi", "http://www.w3.org/2001/XMLSchema-instance");
nsManager.AddNamespace("ixf", "http://www.ixfstd.org/std/ns/core/1.0");
nsManager.AddNamespace("NS1", "CATIA/V6/Electrical/1.0");
nsManager.AddNamespace("NS2", "http://www.ixfstd.org/std/ns/core/classBehaviors/links/1.0");
//Get all wire objects
XmlNodeList wires = xlDocument.SelectNodes("descendant::ixf:object[#xsi:type = \"tns:Wire\"]", nsManager);
foreach (XmlNode wire in wires)
{
string wireName;
string wireLength;
XmlNode node = wire.SelectSingleNode("./tns:Name", nsManager);
wireName = node.InnerText;
XmlNode node1 = wire.SelectSingleNode("./NS1:Wire/NS1:Length", nsManager);
wireLength = node1.InnerText;
}
I can get the wireName value without any problems but the Length element selection always returns 0 matches and I can not figure out why. I also tried to only select the Wire element using the same syntax as the Name element ./NS1:Wire but that also returns 0 matches.
Your XML declares
xmlns:NS1="CATIA/V5/Electrical/1.0"
^^
Your C# declares a different namespacem
nsManager.AddNamespace("NS1", "CATIA/V6/Electrical/1.0")
^^
Make sure both namespaces match exactly.
Regarding your comment asking about the use of version numbers in namespaces...
It is an unfortunately common but certainly not widely accepted practice to include a version number in an XML namespace. Realize that by doing so, you're effectively saying that every namespaced XML component (element or attribute) should now be considered to differ from its counterpart in the old namespace. This is rarely what you want.
See also
Should I use a Namespace of an XML file to identify its version
What are the best practices for versioning XML schemas?
I have an xml file generated by Vector CANeds. This file contains information about CANopen Objects I want to read with my tool written in C#.
The (very basic) structure of the xml is as follows:
<ISO15745ProfileContainer xmlns="http://www.canopen.org/xml/1.0">
<ISO15745Profile>
<ProfileHeader></ProfileHeader>
<ProfileBody xsi:type="ProfileBody_Device_CANopen"</ProfileBody>
</ISO15745Profile>
<ISO15745Profile>
<ProfileHeader></ProfileHeader>
<ProfileBody xsi:type="ProfileBody_CommunicationNetwork_CANopen"</ProfileBody>
</ISO15745Profile>
</ISO15745ProfileContainer>
When I create an XmlNodeList with both ISO15745Profile nodes in it and loop through then i get a strange behaviour. By accessing the subnodes with explicit indexes, everything is as expected. When I am using xpath, allways the first node is used.
Code snippet:
const string filepath = "CANeds1.xdd";
const string s_ns = "//ns:";
var mDataXML = new XmlDocument();
mDataXML.Load(filepath);
var root = mDataXML.DocumentElement;
XmlNamespaceManager nsm = new XmlNamespaceManager(mDataXML.NameTable);
nsm.AddNamespace("ns", root.Attributes["xmlns"].Value);
foreach (XmlNode node in root.ChildNodes) {
Console.WriteLine(" " + node.ChildNodes[1].Attributes["xsi:type"].Value);
Console.WriteLine(" " + node.SelectSingleNode(s_ns + "ProfileBody", nsm).Attributes["xsi:type"].Value);
}
Console output:
ProfileBody_Device_CANopen
ProfileBody_Device_CANopen
ProfileBody_CommunicationNetwork_CANopen
ProfileBody_Device_CANopen
Since node references the 2nd node, the last output should be commNetwork to.
Does somebody see my mistake? I have already tried to rename one of the "ISO15745Profile" nodes but this did not change the outcome. I may have messed up something with the namespace...
Some more explanation to the answer given in the comments:
The important point is the // XPath expression. The definition from MSDN says:
Recursive descent; searches for the specified element at any depth. When this path operator appears at the start of the pattern, it indicates recursive descent from the root node.
This means an expression starting with // will always search for occurences the entire document, even if it's called from a specific child note. That's why SelectSingleNode will always return the first match in the entire document.
To search relative to the node that calls the selection method there is the . operator which indicates the current context.
Put together, an expression starting with .// will search for all occurrences of the following pattern, beginning at the current node.
In the specific case, this means changing //ns: to .//ns: to get the expected result.
This question already has an answer here:
How to Select XML Nodes with XML Namespaces from an XmlDocument?
(1 answer)
Closed 5 years ago.
This a simplified version of a more complex XML that I need to manage with C#.
The problem is that when I try to access to a tag within a namespace, the XPATH does not work.
XmlDocument xmlDoc = new XmlDocument();
xmlDoc.LoadXml("<s:Body xmlns:s=\"sssssss\"><s:SessionID>abcde</s:SessionID></s:Body>");
string xpath = "//*[local-name()='s:SessionID']";
Context.UserLogger.Info(xmlDoc.SelectSingleNode(xpath).InnerText);
//Object reference not set to an instance of an object
But the code works perfect without the colon on the tag.
XmlDocument xmlDoc = new XmlDocument();
xmlDoc.LoadXml("<s:Body xmlns:s=\"sssssss\"><SessionID>abcde</SessionID></s:Body>");
string xpath = "//*[local-name()='SessionID']";
Context.UserLogger.Info(xmlDoc.SelectSingleNode(xpath).InnerText);
//abcde
I have ensured on a XPATH validator that the "//*[local-name()='s:SessionID']" works fine.
What I am missing?
Thanks in advance,
I have read info about XmlNamespaceManager but I would prefer to use "direct" paths. The XML is full of NameSpaces and it is dynamic, so its the structure changes quite often.
the function local-name() returns only the local part of a tag name that in your case is exactly SessionID that's why the expression '//*[local-name()='s:SessionID']' doesn't work (you need to compare qualified names not just strings)
From your question it seems to me that your are interested in selecting the SessionsID elements, if it's so use just the xpath expression
string xpath = "//s:SessionID";
if it doesn't works then you probably need to bound the prefix s with the namespace uri s="sssssss" (take from your example)
I need to get a list of tags that contain a specific attribute. I am using DITA xml and I need to find out all tags that has a href attribute.
The problem here is that the attribute may be inside any tag so XPath will not work in this case. For example, an image tag may contain a href, a topicref tag may contain a href, and so on.
So I need to get a XmlNodeList (as returned by the getElementByTagName method). Ideally I need a method getElementByAttributeName that should return XmlNodeList.
I might have misunderstood your problem here, but I think you could possibly use an XPath expression.
var nodes = doc.SelectNodes("//*[#href='pic1.jpg']");
The above should return all elements with href='pic1.jpg', where doc is the XmlDocument
If you're on C#, then the following approach might work for you:
XDocument document = XDocument.Load(xmlReader);
XAttribute xa = new XAttribute("href", "pic1.jpg");
var attrList = document.Descendants().Where (d => d.Attributes().Contains(xa));
So I'm trying to parse the following XML document with C#, using System.XML:
<root xmlns:n="http://www.w3.org/TR/html4/">
<n:node>
<n:node>
data
</n:node>
</n:node>
<n:node>
<n:node>
data
</n:node>
</n:node>
</root>
Every treatise of XPath with namespaces tells me to do the following:
XmlNamespaceManager mgr = new XmlNamespaceManager(xmlDoc.NameTable);
mgr.AddNamespace("n", "http://www.w3.org/1999/XSL/Transform");
And after I add the code above, the query
xmlDoc.SelectNodes("/root/n:node", mgr);
Runs fine, but returns nothing. The following:
xmlDoc.SelectNodes("/root/node", mgr);
returns two nodes if I modify the XML file and remove the namespaces, so it seems everything else is set up correctly. Any idea why it work doesn't with namespaces?
Thanks alot!
As stated, it's the URI of the namespace that's important, not the prefix.
Given your xml you could use the following:
mgr.AddNamespace( "someOtherPrefix", "http://www.w3.org/TR/html4/" );
var nodes = xmlDoc.SelectNodes( "/root/someOtherPrefix:node", mgr );
This will give you the data you want. Once you grasp this concept it becomes easier, especially when you get to default namespaces (no prefix in source xml), since you instantly know you can assign a prefix to each URI and strongly reference any part of the document you like.
The URI you specified in your AddNamespace method doesn't match the one in the xmlns declaration.
If you declare prefix "n" to represent the namespace "http://www.w3.org/1999/XSL/Transform", then the nodes won't match when you do your query. This is because, in your document, the prefix "n" refers to the namespace "http://www.w3.org/TR/html4/".
Try doing mgr.AddNamespace("n", "http://www.w3.org/TR/html4/"); instead.