I have a simple XML
<AllBands>
<Band>
<Beatles ID="1234" started="1962">greatest Band<![CDATA[lalala]]></Beatles>
<Last>1</Last>
<Salary>2</Salary>
</Band>
<Band>
<Doors ID="222" started="1968">regular Band<![CDATA[lalala]]></Doors>
<Last>1</Last>
<Salary>2</Salary>
</Band>
</AllBands>
However ,
when I want to reach the "Doors band" and to change its ID :
using (var stream = new StringReader(result))
{
XDocument xmlFile = XDocument.Load(stream);
var query = from c in xmlFile.Elements("Band")
select c;
...
query has no results
But
If I write xmlFile.Elements().Elements("Band") so it Does find it.
What is the problem ?
Is the full path from the Root needed ?
And if so , Why did it work without specify AllBands ?
Does the XDocument Navigation require me to know the full level structure down to the required element ?
Elements() will only check direct children - which in the first case is the root element, in the second case children of the root element, hence you get a match in the second case. If you just want any matching descendant use Descendants() instead:
var query = from c in xmlFile.Descendants("Band") select c;
Also I would suggest you re-structure your Xml: The band name should be an attribute or element value, not the element name itself - this makes querying (and schema validation for that matter) much harder, i.e. something like this:
<Band>
<BandProperties Name ="Doors" ID="222" started="1968" />
<Description>regular Band<![CDATA[lalala]]></Description>
<Last>1</Last>
<Salary>2</Salary>
</Band>
You can do it this way:
xml.Descendants().SingleOrDefault(p => p.Name.LocalName == "Name of the node to find")
where xml is a XDocument.
Be aware that the property Name returns an object that has a LocalName and a Namespace. That's why you have to use Name.LocalName if you want to compare by name.
You should use Root to refer to the root element:
xmlFile.Root.Elements("Band")
If you want to find elements anywhere in the document use Descendants instead:
xmlFile.Descendants("Band")
The problem is that Elements only takes the direct child elements of whatever you call it on. If you want all descendants, use the Descendants method:
var query = from c in xmlFile.Descendants("Band")
My experience when working with large & complicated XML files is that sometimes neither Elements nor Descendants seem to work in retrieving a specific Element (and I still do not know why).
In such cases, I found that a much safer option is to manually search for the Element, as described by the following MSDN post:
https://social.msdn.microsoft.com/Forums/vstudio/en-US/3d457c3b-292c-49e1-9fd4-9b6a950f9010/how-to-get-tag-name-of-xml-by-using-xdocument?forum=csharpgeneral
In short, you can create a GetElement function:
private XElement GetElement(XDocument doc,string elementName)
{
foreach (XNode node in doc.DescendantNodes())
{
if (node is XElement)
{
XElement element = (XElement)node;
if (element.Name.LocalName.Equals(elementName))
return element;
}
}
return null;
}
Which you can then call like this:
XElement element = GetElement(doc,"Band");
Note that this will return null if no matching element is found.
The Elements() method returns an IEnumerable<XElement> containing all child elements of the current node. For an XDocument, that collection only contains the Root element. Therefore the following is required:
var query = from c in xmlFile.Root.Elements("Band")
select c;
Sebastian's answer was the only answer that worked for me while examining a xaml document. If, like me, you'd like a list of all the elements then the method would look a lot like Sebastian's answer above but just returning a list...
private static List<XElement> GetElements(XDocument doc, string elementName)
{
List<XElement> elements = new List<XElement>();
foreach (XNode node in doc.DescendantNodes())
{
if (node is XElement)
{
XElement element = (XElement)node;
if (element.Name.LocalName.Equals(elementName))
elements.Add(element);
}
}
return elements;
}
Call it thus:
var elements = GetElements(xamlFile, "Band");
or in the case of my xaml doc where I wanted all the TextBlocks, call it thus:
var elements = GetElements(xamlFile, "TextBlock");
Related
I'm trying to obtain the relevant XML attribute based on the value but I cannot get it to work.
What I am trying to achieve is based on the returned value I want to output the elements name.
Where am I going wrong?
Here's my code so far:
XML:
<addresses>
<address name="house 1">No 1</ipaddress>
<address name="house 2">Flat 3</ipaddress>
<address name="house 3">Siccamore Drive</ipaddress>
</addresses>
C#:
string configPath = _AppPath + #"\HouseAddresses.xml";
XDocument addressXdoc = XDocument.Load(configPath);
XElement addressXmlList = addressXdoc.Element("traplistener");
foreach (XNode node in addressXmlLst.Element("addresses").Descendants())
{
PropertyList = ("string")node.Attribute("name");
}
The XNode type can be seen as a "base". As the documentation states, it represents the abstract concept of a node (element, comment, document type, processing instruction, or text node) in the XML tree. Adding a Attribute property to a text, for example, does not really make sense in the XML context. For that reason, the XNode type does not provide a Attribute property. The XElement type, however, does. Therefore, changing your foreach loop to the version bellow, should do the trick:
foreach (XElement element in addressXmlLst.Element("addresses").Descendants())
{
PropertyList = ("string")element.Attribute("name");
}
A "random" note on your code: since XElement extends XNode the elements returned by Descendants() are correctly converted; for this reason, your problem appears to come from the fact that XNode does not expose a Attribute property, when, in fact, it originates from an unnecessary type conversion.
As an improvement, I would suggest the following:
foreach (XElement element in addressXmlLst.Element("addresses").Descendants())
{
//check if the attribute is really there
//in order to prevent a "NullPointerException"
if (element.Attribute("name") != null)
{
PropertyList = element.Attribute("name").Value;
}
}
In addition to Andrei's answer you can also convert the xml to a dictionary directly via LINQ:
var dictionary = addressXmlLst.Element("addresses").Descendants()
.ToDictionary(
element => element.Attribute("name").Value, // the key
element => element.Value // the value
);
This is my XML:
<?xml version="1.0"?>
<formatlist>
<format>
<formatName>WHC format</formatName>
<delCol>ID</delCol>
<delCol>CDRID</delCol>
<delCol>TGIN</delCol>
<delCol>IPIn</delCol>
<delCol>TGOUT</delCol>
<delCol>IPOut</delCol>
<srcNum>SRCNum</srcNum>
<distNum>DSTNum</distNum>
<connectTime>ConnectTime</connectTime>
<duration>Duration</duration>
</format>
<format>
<formatName existCombineCol="1">Umobile format</formatName> //this format
<delCol>billing_operator</delCol>
<hideCol>event_start_date</hideCol>
<hideCol>event_start_time</hideCol>
<afCombineName dateType="DateTime" format="dd/MM/yyyy HH:mm:ss"> //node i want
<name>ConnectdateTimeAFcombine</name>
<combineDate>event_start_date</combineDate>
<combineTime>event_start_time</combineTime>
</afCombineName>
<afCombineName dateType="DateTime" format="dd/MM/yyyy HH:mm:ss"> //node i want
<name>aaa</name>
<combineDate>bbb</combineDate>
<combineTime>ccc</combineTime>
</afCombineName>
<modifyPerfixCol action="add" perfix="60">bnum</modifyPerfixCol>
<srcNum>anum</srcNum>
<distNum>bnum</distNum>
<connectTime>ConnectdateTimeAFcombine</connectTime>
<duration>event_duration</duration>
</format>
</formatlist>
I want to find format with Umobile format then iterate over those two nodes.
<afCombineName dateType="DateTime" format="dd/MM/yyyy HH:mm:ss"> //node i want
<name>ConnectdateTimeAFcombine</name>
<combineDate>event_start_date</combineDate>
<combineTime>event_start_time</combineTime>
</afCombineName>
<afCombineName dateType="DateTime" format="dd/MM/yyyy HH:mm:ss"> //node i want
<name>aaa</name>
<combineDate>bbb</combineDate>
<combineTime>ccc</combineTime>
</afCombineName>
and list all the two node's child nodes. The result should like this:
ConnectdateTimeAFcombine,event_start_date,event_start_time.
aaa,bbb,ccc
How can I do this?
foreach(var children in format.Descendants())
{
//Do something with the child nodes of format.
}
For all XML related traversing, you should get used to using XPath expressions. It is very useful. Even if you could perhaps do something easier in your specific case, it is good practice to use XPath. This way, if your scheme changes at some point, you just update your XPath expression and your code will be up and running.
For a complete example, you can have a look at this article.
You can use the System.Xml namespace APIs along with System.Xml.XPath namespace API. Here is a quick algorithm that will help you do your task:
Fetch the text node containing the string Umobile format using the below XPATH:
XmlNode umobileFormatNameNode = document.SelectSingleNode("//formatName[text()='Umobile format']");
Now the parent of umobileFormatNameNode will be the node that you are interested in:
XmlNode formatNode = umobileFormatNameNode.ParentNode;
Now get the children for this node:
XmlNodeList afCombineFormatNodes = formatNode.SelectNodes("afCombineName");
You can now process the list of afCombineFormatNodes
for(XmlNode xmlNode in afCombineNameFormtNodes)
{
//process nodes
}
This way you can access those elements:
var doc = System.Xml.Linq.XDocument.Load("PATH TO YOUR XML FILE");
var result = doc.Descendants("format")
.Where(x => (string)x.Element("formatName") == "Umobile format")
.Select(x => x.Element("afCombineName"));
Then you can iterate the result this way:
foreach (var item in result)
{
string format = item.Attribute("format").Value.ToString();
string name = item.Element("name").Value.ToString();
string combineDate = item.Element("combineDate").Value.ToString();
string combineTime = item.Element("combineTime").Value.ToString();
}
I have an xml and I want to append an attribute to each element in xml file.
IEnumerable<XElement> childList = from el in xml.Elements()
select el;
textBox1.Text = childList.ToString();
foreach (XElement el in childList)
{
el.Add(new XAttribute("Liczba_Potomkow", "dziesiec"));
textBox1.Text = el.ToString();
xml.Save("Employees.xml");
}
unfortunately, when I open the file only the first line seems to be affected. (only first elements gets new attribute). Why is so ?
I assume xml is an XDocument? If so, you're calling Elements() directly on the parent of the root element - so the only element it finds will be the root element itself.
If you want to do something for all elements in the document, you should use the Descendants() method.
Additionally, your query expression is pointless - you might as well just use xml.Elements() - and I really don't think you should be saving in a loop.
I think you just want:
foreach (var element in xml.Descendants())
{
element.Add(new XAttribute("Liczba_Potomkow", "dziesiec"));
}
xml.Save("Employees.xml");
Is it possible to get the path of the current XElement in an XDocument? For example, if I'm iterating over the nodes in a document is there some way I can get the path of that node (XElement) so that it returns something like \root\item\child\currentnode ?
There's nothing built in, but you could write your own extension method:
public static string GetPath(this XElement node)
{
string path = node.Name.ToString();
XElement currentNode = node;
while (currentNode.Parent != null)
{
currentNode = currentNode.Parent;
path = currentNode.Name.ToString() + #"\" + path;
}
return path;
}
XElement node = ..
string path = node.GetPath();
This doesn't account for the position of the element within its peer group though.
I know the question is old, but in case someone wants to get a simple one liner:
XElement element = GetXElement();
var xpath = string.Join ("/", element.AncestorsAndSelf().Reverse().Select(a => a.Name.LocalName).ToArray());
Usings:
using System.Linq;
using System.Xml.Linq;
Depending on how you want to use the XPath. In either case you'll need to walk tree up yourself and build XPath on the way.
If you want to have readable string for dispaly - just joining names of prent nodes (see BrokenGlass suggestion) works fine
If you want select later on the XPath
positional XPath (specify position of each node in its parent) is one option (something like //[3]/*). You need to consider attributes as special case as there is no order defined on attributes
XPath with pre-defined prefixes (namespace to prefix need to be stored separately) - /my:root/my:child[3]/o:prop1/#t:attr3
XPath with inlined namespaces when you want semi-readable and portable XPath /*[name()='root' & namespace-uri()='http://my.namespace']/.... (see specification for name and namespace-uri functions http://www.w3.org/TR/xpath/#function-namespace-uri)
Note that special nodes like comments and processing instructions may need to be taken into account if you want truly generic version of the XPath to a node inside XML.
How to get a value of XElement without getting child elements?
An example:
<?xml version="1.0" ?>
<someNode>
someValue
<child>1</child>
<child>2</child>
</someNode>
If i use XElement.Value for <someNode> I get "somevalue<child>1</child><child>2<child>" string but I want to get only "somevalue" without "<child>1</child><child>2<child>" substring.
You can do it slightly more simply than using Descendants - the Nodes method only returns the direct child nodes:
XElement element = XElement.Parse(
#"<someNode>somevalue<child>1</child><child>2</child></someNode>");
var firstTextValue = element.Nodes().OfType<XText>().First().Value;
Note that this will work even in the case where the child elements came before the text node, like this:
XElement element = XElement.Parse(
#"<someNode><child>1</child><child>2</child>some value</someNode>");
var firstTextValue = element.Nodes().OfType<XText>().First().Value;
There is no direct way. You'll have to iterate and select. For instance:
var doc = XDocument.Parse(
#"<someNode>somevalue<child>1</child><child>2</child></someNode>");
var textNodes = from node in doc.DescendantNodes()
where node is XText
select (XText)node;
foreach (var textNode in textNodes)
{
Console.WriteLine(textNode.Value);
}
I think what you want would be the first descendant node, so something like:
var value = XElement.Descendents.First().Value;
Where XElement is the element representing your <someNode> element.
You can specifically ask for the first text element (which is "somevalue"), so you could also do:
var value = XElement.Descendents.OfType<XText>().First().Value;