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.
Related
I have been trying to deserialize the InnerXML into a class and for some reason the XML keeps changing shape and however many times I try to get the class right it seems to change shape again.
So I have given up and decided to try another method.
Is it possible to retrieve the value of a parameter within the InnerXML manually using c#?
Say for example, my XML innerXML looked like this:
<Timestamp>2014-08-22T21:45:00Z</Timestamp>
<Subscriber>https://www.dogdoza.co.uk</Subscriber>
<Order>
<OrderID>111867</OrderID>
<InvoiceNumber>DOZA-9725410</InvoiceNumber>
<CustomerID>4542</CustomerID>
Is it possible to pull out say the value of Subscriber
If this is possible I can just pull out the values I want manually. Not ideal, but there are only about 10...
I have looked around but not managed to find any code I can get working..
Can anyone please give me any guidance?
Thanks
You can do achieve what you want using LINQ to XML:
XElement myXml = XElement.Load(#"XmlLocationHere");
XElement subscriber = myXml.Descendants("Subscriber").FirstOrDefault();
XElement.Descendants returns a collection of the descendant elements for this document or element, in document order. This method will return an IEnumerable<XElement>, since there might be more than one "Subscriber" element, but in your case, we choose FirstOrDefault, which returns the first occurrence.
Try loading your XML into an XDocument. Then try to use XPathSelectElement to find the specific value you want.
It could be that you need to wrap your inner xml into a root element, because it doesn't accept multiple roots.
Pseudo example:
// set up your xml document
string xml = "<rootelement>" + myInnerXml + "</rootelement>";
XDocument doc = new XDocument();
doc.Parse(xml);
XElement subscriber = doc.XPathSelectElement("/rootelement/Subscriber");
string value = subscriber.Value;
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).
<Document>
<Heading1>
<text>Heading Title</text>
<para>para1</para>
<para>para2</para>
<para>para3</para>
</Heading1>
<Heading1>
<text>2nd Heading Title</text>
<para>para4</para>
<para>para5</para>
<para>para6</para>
<Heading2>
<text>3rd Heading Title</text>
<para>para4</para>
<para>para5</para>
</Heading2>
</Heading1>
</Document>
This is XML Document. Now, i want to parse this XML file using C# (4.0). Here, I want to get all the Heading1 elements without using that element name in my program. For example, don't use document.GetElementsByTagName("Heading1");. How i get it. Guide me get out of this issue.
Thanks & Regards.
Using LINQ to XML, you can do:
var headings = yourXDocument.Root.Elements();
Using Nodes() instead of Elements() will also return text nodes and comments, which is apparently not what you want.
You can access the child elements of the document or element through the Elements() method if using LINQ to XML.
XDocument doc = ...;
var query = doc.Root.Elements();
If you're using XmlDocument, this works:
var elements = doc.SelectNodes("/*/*");
That finds all child elements of the top-level element irrespective of any of their names. It's usually safer to specify the names if you know them, so that elements with unexpected names don't get returned in your list - use /Document/Heading1 to do this.
I'm trying to remove a specific node from a XmlNodeList named listaWidths. This specific list has 5 items before I use RemoveChild(). But, after the RemoveChild() statement, the list stays only with 1 item.
XmlNodeList listaWidths = xmlDoc.SelectNodes("/MsBuild:Report/MsBuild:Body/MsBuild:ReportItems/MsBuild:Tablix/MsBuild:TablixBody/MsBuild:TablixColumns/*", nsmgr);
int indexEpoca = 0;
XmlNode node = listaWidths[indexEpoca];
XmlNode parent = listaWidths[indexEpoca].ParentNode;
parent.RemoveChild(node);
This is a RDL Reporting Services XML.
The specific XML code is here:
<Tablix Name="Tablix3">
<TablixBody>
<TablixColumns>
<TablixColumn>
<Width>1.602in</Width>
</TablixColumn>
<TablixColumn>
<Width>1.61in</Width>
</TablixColumn>
<TablixColumn>
<Width>1.6323in</Width>
</TablixColumn>
<TablixColumn>
<Width>1.6023in</Width>
</TablixColumn>
<TablixColumn>
<Width>1.6033in</Width>
</TablixColumn>
</TablixColumns>
(...)
I've tried every combination possible, with no luck whatsoever. What am I doing wrong?
Thank you.
The documentation of SelectNodes clearly says: "The XmlNodeList object returned by this method will be valid while the underlying document remains unchanged. If the underlying document changes, unexpected results may be returned (no exception will be thrown)."
So what you experience with your XmlNodeList returned from SelectNodes after you manipulate the document might not be what you expect but is in line with the documentation. You will have to call SelectNodes again to get a new XmlNodeList if you manipulate the document.
In my view the designers of the DOM implementation in the .NET framework made a mistake by using XmlNodeList as an abstract class for concrete implementation with quite different behaviour. If you use e.g. ChildNodes then you get a "live" node list in line with what the W3C DOM specification requires so in that case a document change automatically changes the node list (if needed). However SelectNodes returns a node list with a quite different behaviour, as you experienced.
I've got a XmlNodeList which I need to have it in a format that I can then re-use within a XSLT stylesheet by calling it from a C# extension method.
Can anyone help? I have read that it might have something to do with using a XPathNavigator but I'm still a bit stuck.
I had to solve this issue myself a couple of years ago. The only way I managed it was to create an XML fragment containing the nodes in the node list and then passing in the children of the fragment.
XsltArgumentList arguments = new XsltArgumentList();
XmlNodeList nodelist;
XmlDocument nodesFrament = new XmlDocument();
XmlNode root = nodesFragment.CreateElement("root");
foreach (XmlNode node in nodeList)
{
root.AppendChild(node);
}
nodesFragment.AppendChild(root);
arguments.AddParam("argumentname", string.Empty, nodesFragment.CreateNavigator().SelectChildren(XPathNodeType.All));
Then you need to make sure you have the corresponding argument in your XSLT, of course.
Note that you probably don't need the additional XmlDocument. You could just call CreateNavigator() on the root XmlNode instance and use your existing XmlDocument for creating the element (I wrote this code some time ago and I've learned more since then - but I know the code above works, I haven't tried any alternatives).
The note at the end was the most useful, I had infact transformed the XmlNodeList into a XmlDocument already so could just use the Navigator on there and create it as a XPathNodeIterator.
Thanks for you help!
Didn't succeed with the answer provided before.
Using AppendChild() to add previously selected nodes of XmlNodeList to a new document resulted in exception on trying to append nodes originating from a different document context. Several trials to fix this included adding my custom default namespace selected nodes in list are bound to. Finally I dropped the approach completely and switched the way I select nodes into XmlNodeList instances.
Instead of
myXmlNode.SelectNodes( xpath, nsmgr )
I'm using
myXmlNode.CreateNavigator().Select( xpath, nsmgr )
to get an XPathNodeIterator instead of XmlNodeList. The resulting XPathNodeIterator of second code is now properly added as parameter value to XsltArgumentsList.