In a project I am working on, I just finished writing an XSD for my XML so other engineers could work on the XML easier. Along with this XSD came XML namespaces. In my current parsing code, I have been using something like this:
XElement element = xmlRoot.Element(XML.ELEMENT_NAME);
With XML being a class full of constants that is used throughout the program for XML input and output. But, now that namespaces are being used, this doesn't work anymore. The obvious, but barely elegant, solution is to go in and make all of the parsing code look like this:
XElement element = xmlRoot.Element(XML.NAMESPACE + XML.ELEMENT_NAME);
Thinking about it more, it would look a lot better to go off and define an extension method to add in this namespace and return the XElement. This idea would get the code looking something like this:
XElement element = xmlRoot.GetMyElement(XML.ELEMENT_NAME);
These ideas are what I have come up with so far to deal with the namespace issue.
Basically, my question here is this:
Is there a better method for parsing XElements with a known, constant namespace? If so, what is it?
Well, no one's provided an alternative, and I've already implemented this in the code. So, I'm going to go ahead and put this in as an answer so I can close this out.
I went ahead and used the extension method that automatically added in the namespace. Note that this only works if you have a constant namespace! Otherwise, you may want to add another argument to your extension method simply to avoid doing the weird namespace concatenation.
public static XElement
GetNamespaceElement(this XElement element, string ns, string name)
{
XNamespace n = new XNamespace();
n.NamespaceName = ns;
return element.Element(n + name);
}
Related
I don't have experience with this so perhaps I'm using the wrong terminology.
The scenario is this: I'm serializing a class instance to a file using the code from https://stackoverflow.com/a/12309136/939213 . But at some point I might want to change the class a bit, so I would like to insert an int into the file telling the program what version of the class this is.
I tried serializing the int and the class into the same file but discovered that's impossible, so I'm now thinking of having an int property in the class for that, and reading that first, in order to know what class should be deserialized.
So how do I read that int alone?
EDIT: For example, to read the myInt in this:
<MyClass xml...>
<myInt>10</myInt>
<myString>abc</myString>
</MyClass>
You need to provide some example xml if you want a specific answer, otherwise you can check out Linq-To-Xml for more info.
A comment lead me to a solution:
XDocument xdoc = XDocument.Load(path);
int answer = (int)xdoc.Descendants("myInt").ToArray()[0];
When processing xmlDocument with xPath using, for example, SelectNodes, there's a behavior in documents, which contain any namespace declarations, which I consider a bug:
If an xml document contains any namespaces declarations (e g xmlns=..... or something similar), the xquerry will always come out empty.
A lazy-ass way of dealing with this is to run following code on the xml text before loading it into the XmlDocumennt:
pg = Regex.Replace(pg, #"xmlns\s*\=\s*""[^""]*""", "");
pg = Regex.Replace(pg, #"xmlns\s*\=\s*'[^']*'", "");
We can also use XmlNamespaceManager to pall namespace information into the xpath call. I find both approaches cumbersome (I usually don't know the namespaces of the documents that the software will be working with, and, also, I don't really care).
Is there an easy to use way to disable this behavior of Microsoft's XPath parser, which also "feels" right?
If you really don't care about the namespaces then I'd say stripping them from the XML would seem to feel right. I'd not recommend such an approach in a production environment though, where you probably should care about namespaces.
I have few XML files which I would be using in my C# code.
So far I have been using XPATH for accessing the XML node / attributes
Question is what advantage would I get if i convert the XML to Class file (XSD.EXE) and use it in terms of maintainability and code readability.
In both the cases I know if I add or remove some nodes, code needs to be changed
In my case the DLL goes into GAC.
I am just trying to get your views
Cheers,
Karthik
The beauty of converting your XML to XSD and then to a C# class is the ease in which you can grab yet another file. Your code would be something like:
XmlSerializer ser = new XmlSerializer(typeof(MyClass));
FileStream fstm = new FileStream(#"C:\mysample.xml", FileMode.Open, FileAccess.Read);
MyClass result = ser.Deserialize(fstm) as MyClass;
if(result != null)
{
// do whatever you want with your new class instance!
}
With these few lines, you now have an object that represent exactly what your XML contained, and you can access its properties as properties on the object instance - much easier than doing lots of complicated XPath queries into your XML, in my opinion.
Also, thanks to the fact you now have a XSD, you can also easily validate incoming XML files to make sure they actually do correspond to the contract defined - which causes less constant error-checking in your code (you don't have to check after each XPath to see whether there's any node(s) that actually match that expression etc.).
I have deserialized an xml file into a C# object and have an "object" containing a specific node I have selected from this file.
I need to check if this node has child nodes. I do not know the specific type of the object at any given time.
At the moment I am just re-serializing the object into a string, and loading it into an XmlDocument before checking the HasChildNodes property, however when I have thousands of nodes to check this is extremely resource intensive and slow.
Can anyone think of a better way I can check if the object I have contains child nodes?
Many thanks :)
try using Linq2xml, it has a class called XElement (or XDocument) which are much easier to use then the XmlDocument.
something like this:
XElement x = XElement.Load("myfile.xml");
if (x.Nodes.Count() > 0)
{
// do whatever
}
much less code, much more slick, very readable.
if you have the xml already as a string, you can replace the Load with the Parse function.
I guess you could reverse the process (looking at all public members/properties that aren't marked [XmlIgnore], aren't null, and don't have a public bool ShouldSerialize*() that returns false or any of the other patterns), but this seems a lot of work...
I'm new to .net and c#, so I want to make sure i'm using the right tool for the job.
The XML i'm receiving is a description of a directory tree on another machine, so it go many levels deep. What I need to do now is to take the XML and create a structure of objects (custom classes) and populate them with info from the XML input, like File, Folder, Tags, Property...
The Tree stucture of this XML input makes it, in my mind, a prime candidate for using recursion to walk the tree.
Is there a different way of doing this in .net 3.5?
I've looked at XmlReaders, but they seem to be walking the tree in a linear fashion, not really what i'm looking for...
The XML i'm receiving is part of a 3rd party api, so is outside my control, and may change in the futures.
I've looked into Deserialization, but it's shortcomings (black box implementation, need to declare members a public, slow, only works for simple objects...) takes it out of the list as well.
Thanks for your input on this.
I would use the XLINQ classes in System.Xml.Linq (this is the namespace and the assembly you will need to reference). Load the XML into and XDocument:
XDocument doc = XDocument.Parse(someString);
Next you can either use recursion or a pseudo-recursion loop to iterate over the child nodes. You can choose you child nodes like:
//if Directory is tag name of Directory XML
//Note: Root is just the root XElement of the document
var directoryElements = doc.Root.Elements("Directory");
//you get the idea
var fileElements = doc.Root.Elements("File");
The variables directoryElements and fileElements will be IEnumerable types, which means you can use something like a foreach to loop through all of the elements. One way to build up you elements would be something like this:
List<MyFileType> files = new List<MyFileType>();
foreach(XElelement fileElement in fileElements)
{
files.Add(new MyFileType()
{
Prop1 = fileElement.Element("Prop1"), //assumes properties are elements
Prop2 = fileElement.Element("Prop2"),
});
}
In the example, MyFileType is a type you created to represent files. This is a bit of a brute-force attack, but it will get the job done.
If you want to use XPath you will need to using System.Xml.XPath.
A Note on System.Xml vs System.Xml.Linq
There are a number of XML classes that have been in .Net since the 1.0 days. These live (mostly) in System.Xml. In .Net 3.5, a wonderful, new set of XML classes were released under System.Xml.Linq. I cannot over-emphasize how much nicer they are to work with than the old classes in System.Xml. I would highly recommend them to any .Net programmer and especially someone just getting into .Net/C#.
XmlReader isn't a particularly friendly API. If you can use .NET 3.5, then loading into LINQ to XML is likely to be your best bet. You could easily use recursion with that.
Otherwise, XmlDocument would still do the trick... just a bit less pleasantly.
This is a problem which is very suitable for recursion.
To elaborate a bit more on what another poster said, you'll want to start by loading the XML into a System.Xml.XmlDocument, (using LoadXml or Load).
You can access the root of the tree using the XmlDocument.DocumentElement property, and access the children of each node by using the ChildNodes property. Child nodes returns a collection, and when the Collection is of size 0, you know you'll have reached your base case.
Using LINQ is also a good option, but I'm unable to elaborate on this solution, cause I'm not really a LINQ expert.
As Jon mentioned, XmlReader isn't very friendly. If you end up having perf issues, you might want to look into it, but if you just want to get the job done, go with XmlDocument/ChildNodes using recursion.
Load your XML into an XMLDocument. You can then walk the XMLDocuments DOM using recursion.
You might want to also look into the factory method pattern to create your classes, would be very useful here.