Using the example below, I would like to use xPath to find the first occurence of two different elements. For example, I want to figure out if b or d appears first. We can obviously tell that b appears before d (looking top-down, and not at the tree level). But, how can I solve this using xpath?
<a>
<b>
</b>
</a>
<c>
</c>
<d>
</d>
Right now, I find the node (b and d in this case) by getting the first element in the nodeset, which I find using the following code:
String xPathExpression = "//*[local-name()='b']";
XPathNodeIterator nodeSet = (XPathNodeIterator)navigator.Evaluate(xPathExpression);
and
String xPathExpression = "//*[local-name()='d']";
XPathNodeIterator nodeSet = (XPathNodeIterator)navigator.Evaluate(xPathExpression);
Now using xpath, I just can't figure out which comes first, b or d.
You want to scan the tree in document order (the order the elements occur). As though by chance this is the default search order, and all you've got to do is select the first element which is a <b/> or <d/> node:
//*[local-name() = 'b' or local-name() = 'd'][1]
If you want the name, add another local-name(...) call:
local-name(//*[local-name() = 'b' or local-name() = 'd'][1])
If you wanted to use LINQ to XML to solve the same solution you can try the following:
XDocument xmlDoc = new XDocument(filepath);
XElement first = (from x in xmlDoc.Descendants()
where x.Name == "b" || x.Name == "d"
select x).FirstOrDefault();
Now you can run a simple if statement to determine if "b" or "d" was the first element found that matches our criteria.
if(first.Name.Equals("b")
//code for b being first
else if(first.Name.Equals("d")
//code for d being first
Per a commentator's suggestion your code would is cleaner to use a lambda expression instead of a full LINQ query, but this can sometimes be confusing if you are new to LINQ. The following is the exact same query for my XElement assignment above:
XElement first = xmlDoc.Descendants().FirstOrDefault(x => x.Name == "b" || x.Name == "d");
I hope that's what you're looking for if you were open to not using xpath.
This XPath expressions would work:
//*[local-name()='b' or local-name()='d'][1]
Or for a shorter solution, you could try this:
(//b|//d)[1]
Both expressions will select either b elements or d elements, in the order in which they appear, and only select the first element from the result set.
Related
I have this linq expression that I need to convert to XPath select element:
XElement transIdElement = (from criteria in searchCriteria.Descendants("CRITERIA")
where criteria.Element("DataPointName).Value == "TransactionNumber"
select criteria.Element("CriteriaComparisonValue")).FirstOrDefault();
and I tried with this:
var transIdElement = searchCriteria.XPathSelectElement("//CRITERIA/DataPointName[text() = 'TransactionNumber']/CriteriaComparisonValue");
but I get null as result.
XML sample is:
<SEARCH>
<ADVANCED_CRITERIA>
<CRITERIA>
<DataPointName>TransactionNumber</DataPointName>
<CriteriaComparisonValue>12457845</CriteriaComparisonValue>
</CRITERIA>
</ADVANCED_CRITERIA>
</SEARCH>
void Main()
{
string xml = #"<SEARCH>
<ADVANCED_CRITERIA>
<CRITERIA>
<DataPointName>TransactionNumber</DataPointName>
<CriteriaComparisonValue>12457845</CriteriaComparisonValue>
</CRITERIA>
</ADVANCED_CRITERIA>
</SEARCH>";
var searchCriteria = XElement.Parse(xml);
searchCriteria.XPathSelectElements("//CRITERIA[DataPointName='TransactionNumber']/CriteriaComparisonValue").Dump();
}
Use .. to access parent::node() and try
//CRITERIA/DataPointName[text() = 'TransactionNumber']/../CriteriaComparisonValue
quick test in LINQpad:
var f = #"c:\temp\x\a.xml";
var searchCrit = XDocument.Load(f);
searchCrit.XPathSelectElement("//CRITERIA/DataPointName[text() = 'TransactionNumber']/../CriteriaComparisonValue").Value.Dump();
produces
12457845
A more accurate XPath translation of your LINQ-to-XML query would be as follow :
//CRITERIA[DataPointName = 'TransactionNumber']/CriteriaComparisonValue
Here is a glimpse of how the above predicate expression (expression in square brackets) works.
DataPointName references child element named "DataPointName" of the context element. In this particular predicate, the context element is CRITERIA.
'TransactionNumber' with quotes surround means literal-string in XPath. When an element compared to a string in XPath, the element is translated into string by calling XPath string() function.
Given this XML:
<InitResponse>
<LottoToken>908ec70b308adf10d04db1478ef9b01b</LottoToken>
<GameInfoList>
<GameInfo>
<Draw>
<gameId>L649</gameId>
<draw>3035</draw>
</Draw>
</GameInfo>
<GameInfo>
<Draw>
<gameId>BC49</gameId>
<draw>2199</draw>
</Draw>
</GameInfo>
</GameInfoList>
</InitResponse>
I need to get the draw number based on a specific gameId. For example if I specify gameID L649 I need to get 3035.
The following works in several online evaluators, but not in C#. It says it cannot find it. Suggestions?
/InitResponse/GameInfoList/GameInfo/Draw/draw[preceding-sibling::gameId='L649']
C# Code I've tried:
XmlNode node = xmlDoc.SelectSingleNode("/InitResponse/GameInfoList/GameInfo/Draw/draw[preceding-sibling::gameId='L649']");
... where xmlDoc is an xmlDocument object loaded with the xml. the node variable ends up with a null value which seems to indicate there was no match found.
Here is xpath (with Linq)
var xdoc = XDocument.Load(path_to_xml);
string xpath = "/InitResponse/GameInfoList/GameInfo/Draw[gameId='L649']/draw";
var draw = xdoc.XPathSelectElement(xpath);
if (draw != null) // check if draw with gameId found in xml
value = (int)draw;
Also you can use pure Linq to Xml (but in this case xpath looks more compact):
var draw = xdoc.Descendants("GameInfo")
.SelectMany(g => g.Elements("Draw"))
.SingleOrDefault(d => (string)d.Element("gameId") == "L649");
if (draw != null)
value = (int)draw.Element("draw");
Using XmlDocument
I didn't saw something wrong in your XPath statement, look on the following:
(So i guess there is something else that is wrong)
XmlDocument myDoc = new XmlDocument();
String str = #"<InitResponse>
<LottoToken>908ec70b308adf10d04db1478ef9b01b</LottoToken>
<GameInfoList>
<GameInfo>
<Draw>
<gameId>L649</gameId>
<draw>3035</draw>
/Draw>
</GameInfo>
<GameInfo>
<Draw>
<gameId>BC49</gameId>
<draw>2199</draw>
</Draw>
</GameInfo>
</GameInfoList>
</InitResponse>";
myDoc.LoadXml(str);
XmlNode node =
myDoc.SelectSingleNode("/InitResponse/GameInfoList/GameInfo/Draw/draw[preceding-sibling::gameId='L649']");
The node which returns from the result is: 3035
Note: your first note have to be <InitResponse> otherwise it will returns null
I have problem i'm trying to update a specific part of the XML with the linq query but it doesn't work. So i an xml file:
<?xml version="1.0" encoding="utf-8"?>
<DesignConfiguration>
<Design name="CSF_Packages">
<SourceFolder>C:\CSF_Packages</SourceFolder>
<DestinationFolder>C:\Documents and Settings\xxx</DestinationFolder>
<CopyLookups>True</CopyLookups>
<CopyImages>False</CopyImages>
<ImageSourceFolder>None</ImageSourceFolder>
<ImageDesinationFolder>None</ImageDesinationFolder>
</Design>
</DesignConfiguration>
I want to select the part where the part where there is Design name="somethning" and get the descendants and then update the descendants value that means this part:
<SourceFolder>C:\CSF_Packages</SourceFolder>
<DestinationFolder>C:\Documents and Settings\xxx</DestinationFolder>
<CopyLookups>True</CopyLookups>
<CopyImages>False</CopyImages>
<ImageSourceFolder>None</ImageSourceFolder>
<ImageDesinationFolder>None</ImageDesinationFolder>
I have this code:
XDocument configXml = XDocument.Load(configXMLFileName);
var updateData = configXml.Descendants("DesignConfiguration").Elements().Where(el => el.Name == "Design" &&
el.Attribute("name").Value.Equals("CSF_Packages")).FirstOrDefault();
configXml.Save(configXMLFileName);
I'm getting the null data in the updateData varibale. When I'm trying the Descendat's function through QuickWatch it also returns a null value. When I'm checking the configXML variable it has data that is my whole xml. What am I doing wrong?
Try this:
var updateData =
confixXml
.Root //Root Element
.Elements("Design") //All elements under root called Design
.Where(element => (String)element.Attribute("name") == "AFP_GRAFIKA") //Find the one with the name Attribute of AFP_GRAFIKA
.FirstOrDefault(); //Grab the first one it finds or return null.
if (updateData != null)
{
var myElements =
updateData
.Elements(); //All the elements under the Design node
}
XDocument xml = XDocument.Load("");
XElement settings = (from children in xml.Descendants("DesignConfiguration")
where children.Name.Equals("Design") && children.Attribute("name").Equals("CSF_Packages")
select children).FirstOrDefault();
settings.Element("SourceFolder").SetValue("filepath");
settings.Element("CopyImages").SetValue(true);
Ok, so I've managed to fix the problem. I don't know why but it worked. It seems that the Descendants function returns null as a stand alone function but with linq it works. So for my solution only thing what should be done is this:
var updateData = (from s in configXml.Descendants("Design")
where s.Attribute("name").Value == design.DesignName
select s).First();
At first before I sent you my question I've tried this but I didn't have the select s part. Besides when I wrote the where s.Atribute part in the curly brackets I've inserted the design.DesignName object instead of the name of the attribute. So no it works ok. Thanks for your help and everything. Til nex time. Have a nice day/night everyone :)
Because DesignConfiguration was your root node, the Descendants("DesignConfiguration) was returning null. By using the .Descendants("Design"), you were looking at child nodes, not the self.
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");
I have the following XML:
<?xml version="1.0" encoding="UTF-8"?>
<game>
<name>Space Blaster</name>
<description></description>
<version>1</version>
<fullscreen>false</fullscreen>
<width>640</width>
<height>640</height>
<c2release>6900</c2release>
</game>
It's guaranteed to only have 1 game record in it. I'd like to retrieve each property value, this is what I've tried:
string ArcadeXMLLocation = Settings.GamePergatoryLocation + UserID + "/unzipped/arcade.xml";
XDocument loaded = XDocument.Load(ArcadeXMLLocation);
var q = (from c in loaded.Descendants("game") select (string)c.Element("name")).SingleOrDefault();
Response.Write(q.name);
But I can't seem to take any values like this (intellisense hates it!) Can someone show me how it's done?
I think you just need to get the value of the element:
string val = doc.Descendants("game")
.Select(x => x.Element("name").Value).FirstOrDefault();
As a prerequisite to the above, and so intellisense picks it up, make sure that you import the System.Linq and System.Xml.Linq namespaces.
This will get you all the descendants with the tag "game"
You just need the FirstOrDefault() to get the only record if it exists.
var q = from c in loaded.Descendants("game")
select new { Name = c.Element("name").Value
Description = c.Element("description").Value
};
q.FirstOrDefault();
You query is actually correct (tested and worked for me) for extracting the value of the name node - the (string) cast that you are doing will extract the value of the name node as string and not give you the node object itself, this is one of the shortcuts built into Linq to Xml. All that is left is to print out the name:
Response.Write(q);
var q = (from c in loaded.Descendants("game") select (string)c.Element("name")).SingleOrDefault();
Console.WriteLine(q);
is enough. or to avoid the cast
var q = (from c in loaded.Descendants("game") select c.Element("name").Value).SingleOrDefault();
Console.WriteLine(q);