I'm a novice w/ the Linq parsing in .NET. I have probably a simple question that I'm hoping someone can quickly answer for me. I have a huge xml that I've condensed down to figure out why my query fails. I need to parse an element from the xml that's within an node containing an attribute type. The query needs to match the attribute type and return the element value for the element name. However, the problem I'm having is, my xml has d: prefixes before the attribute name and element name and my Linq query just chokes on it. If I remove the d: prefix from the xml and query string, it works and returns the correct values, but with prefixes it doesn't work. Can someone look at my Linq query and see what I'm doing wrong with the prefixes?
Condensed xml code
<root>
<Contact xmlns:c="http://test/common/1.0">
<c:IBase type="d:testInfo" xmlns:d="http://">
<d:ActivityID>00000</d:ActivityID>
</c:IBase>
<c:IBase type="d:testInfo" xmlns:d="http://">
<d:ActivityID>00001</d:ActivityID>
</c:IBase>
</Contact>
</root>
Linq Query
var node = from el in xml.Descendants("IBase")
where
el.Attribute("type").Value == "testInfo"
select el.Element("ActivityID").Value;
foreach ( String s in node )
Console.WriteLine(string.Format("Id= {0}",s));
You have two problems to address here.
You need to specify the namespace as part of the query, as Bradley Uffner mentioned in his comment.
The type actually has a "d:" in it, which is not a namespace since it is in the value of the attribute, so you need to compare against "d:testInfo" and not just "testInfo"
Try the following:
XDocument xml = XDocument.Parse(myXmlString);
XNamespace xnc = "http://test/common/1.0";
XNamespace xnd = "http://";
var node = from el in xml.Descendants(xnc + "IBase")
where
el.Attribute("type").Value == "d:testInfo"
select el.Element(xnd + "ActivityID").Value;
foreach ( String s in node )
Console.WriteLine(string.Format("Id= {0}",s));
Related
Variations of this question have already been asked but I have not found one that can help me with the problem i am having.
Given and XML file of this format:
<TopLevel>
<SecondLevel Name="Name" Color="Blue">
<ChildNode1></ChildNode1>
<ChildNode2></ChildNode2>
</SecondLevel>
<SecondLevel Name="Name2" Color="Red">
...
</SecondLevel>
</topLevel>
I have the value to the attribute Color.
What I would like is to be able to first find the Name corresponding to that color, and then find all the childnodes.
I prefer to use Xelement over XDocument.
This is what I have attempted so far, but with no luck.
XElement xelement = XElement.Load("XmlFile.xml");
IEnumerable<XElement> Name2=
from el in xelement.Elements("SecondLevel")
where el.Attribute("Color") == "Red"
select el;
With the result of that, I will eventually want to format it into a datatable. Is this doable?
You just missing cast of attribute to string (or getting it's value directly - see notes at the end). Also you can select Name attribute value to have sequence of strings instead of XElements:
XElement xelement = XElement.Load("XmlFile.xml");
IEnumerable<string> names =
from el in xelement.Elements("SecondLevel")
where (string)el.Attribute("Color") == "Red" // here
select (string)el.Attribute("Name");
NOTE: You can also access attribute value directly with el.Attribute("Color").Value but that will throw exception if element don't have Color attribute. So casting is more safe, but accessing value can be option if you want your code to fail fast if xml is not valid.
BTW you can also use XPath to get second level elements which have required color:
IEnumerable<XElement> secondLevels =
xelement.XPathSelectElements("SecondLevel[#Color='Red']");
I have an XML file, that contain IDs in an attribute called translatedID.
This attribute exists in almost every element in the doc, so instead of searching for each element one by one, I want to select all the translatedID in the document and run some code on each attribute's value.
The needed result is - replacing the translatedID with some other data.
How can I select ALL the translatedID that exists in my XML document?
Sounds like a great case for LINQ to XML:
XDocument doc = XDocument.Load("doc.xml");
var attributes = doc.Descendants().Attributes("translatedID");
foreach (var attribute in attributes)
{
attribute.Value = DoSomethingWith(attribute.Value);
}
doc.Save("transformed.xml");
(That's assuming you want to change the value of the attribute. If you want to do something else, that's doable - but you'll need to give more information.)
<root>
<data name="ID1"></data>
<data name="ID2"></data>
</root>
XDocument xmlDoc = XDocument.Load(xmlFile);
bool exists = (from elem in xmlDoc.Descendants("root")
where elem.Element("data").Attribute("name").Value == "ID1"
select elem).Any();
It doesn't see that ID1 already exists. What am I doing wrong?
Based on what you've shown, first I have to point out that the XML snippet is not valid XML. The data nodes are not closed.
Assuming this is a valid XML document, it would ultimately depend on what the type is for your variable XMLDoc.
If it was an XDocument, then that code snippet should work and the value of exists would be true. The document contains a descendant called root and it could go about its business.
If it was an XElement on the other hand, then that code snippet should fail and the value of exists would be false. The XMLDoc variable would be referring to the root element already and there clearly isn't any descendants called root.
You should rewrite your query however, maybe something more like this:
// please follow .NET naming conventions and use lowercase for local variables
XDocument xmlDoc = XDocument.Load(xmlFile);
// iterate over the `data` elements, not the `root` elements
bool exists = (from data in xmlDoc.Element("root").Elements("data")
where (string)data.Attribute("name") == "ID1"
select data).Any();
// using the cast is a personal style choice
// using `XAttribute.Value` is fine too in this case
I have xml document like this:
<level1>
<level2>
<level3>
<attribute1>...</attribute1>
<attribute2>false</attribute2>
<attribute3>...</attribute3>
</level3>
<level3>
<attribute1>...</attribute1>
<attribute2>true</attribute2>
<attribute3>...</attribute3>
</level3>
</level2>
<level2>
<level3>
<attribute1>...</attribute1>
<attribute2>false</attribute2>
...
...
...
I'm using c#, and I want to go thru all "level3", and for every "level3", i want to read attribute2, and if it says "true", i want to print the corresponding attribute3 (can be "level3" without these attributes).
I keep the xml in XmlDocument.
Then I keep all the "level3" nodes like this:
XmlNodeList xnList = document.SelectNodes(String.Format("/level1/level2/level3"));
(document is the XmlDocument).
But from now on, I don't know exactly how to continue. I tried going thru xnList with for..each, but nothing works fine for me..
How can I do it?
Thanks a lot
Well I'd use LINQ to XML:
var results = from level3 in doc.Descendants("level3")
where (bool) level3.Element("attribute2")
select level3.Element("attribute3").Value;
foreach (string result in results)
{
Console.WriteLine(result);
}
LINQ to XML makes all kinds of things much simpler than the XmlDocument API. Of course, the downside is that it requires .NET 3.5...
(By the way, naming elements attributeN is a bit confusing... one would expect attribute to refer to an actual XML attribute...)
You can use LINQ to XML and reading this is a good start.
You can use an XPath query. This will give you a XmlNodeList that contains all <attribute3> elements that match your requirement:
var list = document.SelectNodes("//level3[attribute2 = 'true']/attribute3");
foreach(XmlNode node in list)
{
Console.WriteLine(node.InnerText);
}
You can split the above xpath query in three parts:
"//level3" queries for all descendant elements named <level3>.
"[attribute2 = 'true']" filters the result from (1) and only keeps the elements where the child element <attribute2> contains the text true.
"/attribute3" takes the <attribute3> childnode of each element in the result of (2).
I'm writing one of my first C# programs. Here's what I'm trying to do:
Open an XML document
Navigate to a part of the XML tree and select all child elements of type <myType>
For each <myType> element, change an attribute (so <myType id="oldValue"> would become <myType id="newValue">
Write this modified XML document to a file.
I found the XmlDocument.SelectNodes method, which takes an XPath expression as its argument. However, it returns an XmlNodeList. I read a little bit about the difference between an XML node and an XML element, and this seems to explain why there is no XmlNode.SetAttribute method. But is there a way I can use my XPath expression to retrieve a list of XmlElement objects, so that I can loop through this list and set the id attributes for each?
(If there's some other easier way, please do let me know.)
Simply - it doesn't know if you are reading an element or attribute. Quite possibly, all you need is a cast here:
foreach(XmlElement el in doc.SelectNodes(...)) {
el.SetAttribute(...);
}
The SelectNodes returns an XmlNodeList, but the above treats each as an XmlElement.
I am a big fan of System.Xml.Linq.XDocument and the features it provides.
XDocument xDoc = XDocument.Load("FILENAME.xml");
// assuming you types is the parent and mytype is a bunch of nodes underneath
IEnumerable<XElement> elements = xdoc.Element("types").Elements("myType");
foreach (XElement type in elements)
{
// option 1
type.Attribute("id").Value = NEWVALUE;
// option 2
type.SetAttributeValue("id", NEWVALUE);
}
Option 1 or 2 works but I prefer 2 because if the attribute doesn't exist this'll create it.
I'm sitting at my Mac so no .NET for me...
However, I think that you can cast an XmlNode to an XmlElement via an explicit cast.
You should be able to cast the XmlElement to an XmlNode then and get it's children Nodes using something like XmlNode.ChildNodes.