I want to use LINQ to XML in Silverlight 3 since there is no XPath support.
I have kind of got the hang of it. But the project I'm working on will not guarantee that all the XML tags I will be querying for will appear in the result XML file.
Due to this I will not be able to query the overall file as XDocument becase the absence of the tag in one document will jumble up the enumeration.
Is there anyway to typecast an XNode to XDocument? I am asking this as I am not able to query the XNode.
Even with LINQ-to-XML you should be querying by name, so I'm not sure why the absence of any particular tag should "jumble up the enumeration" - simply; you might have some nulls, i.e.
var customer = node.Element("Foo");
// now test for null ;p
You can't cast an arbitrary XNode to an XDocument, but if you are sure it is an element, casting to XElement should provide what you need.
Note also that when value nodes may be missing, you might find it easiest to use the conversion operators:
var auditDate = (DateTime?)e.Element("AuditDate");
if <AuditDate> doesn't exist, this will return an empty Nullable<DateTime> - same approach works for most common value-types, or for strings just convert to string.
Related
First I load the file in a structure
XElement xTree = XElement.Load(xml_file);
Then I create an enumerable collection of the elements.
IEnumerable<XElement> elements = xTree.Elements();
And iterate elements
foreach (XElement el in elements)
{
}
The problem is - when I fail to parse the element (a user made a typo or inserted a wrong value) - how can I report exact line in the file?
Is there any way to tie an element to its corresponding line in the file?
One way to do it (although not a proper one) –
When you find a wrong value, add an invalid char (e.g. ‘<’) to it.
So instead of: <ExeMode>Bla bla bla</ExeMode>
You’ll have: <ExeMode><Bla bla bla</ExeMode>
Then load the XML again with try / catch (System.Xml.XmlException ex).
This XmlException has LineNumber and LinePosition.
If there is a limited set of acceptable values, I believe XML Schemas have the concept of an enumerated type -- so write a schema for the file and have the parser validate against that. Assuming the parser you're using supports Schemas, which most should by now.
I haven't looked at DTDs in decades, but they may have the same kind of capability.
Otherwise, you would have to consider this semantic checking rather than syntactic checking, and that makes it your application's responsibility. If you are using a SAX parser and interpreting the data as you go, you may be able to get the line number; check your parser's features.
Otherwise the best answer I've found is to report the problem using an xpath to the affected node/token rather than a line number. You may be able to find a canned solution for that, either as a routine to run against a DOM tree or as a state machine you can run alongside your SAX code to track the path as you go.
(All the "maybe"s are because I haven't looked at what's currently available in a very long time, and because I'm trying to give an answer that is valid for all languages and parser implementations. This should still get you pointed in some useful directions.)
using XDocument with xpath to parse XML
which one is better in perfomance ?
e.g. To search for tag and get value in xml
tags = xmlDoc.Descendants(xmlTag);
or
xml.SelectSingleNode("//root/node")
So which one will be faster?
XPath doesn't parse XML... it's a query language used on top of any other XML API which supports it. (For example, you can use XPath over XmlDocument or XDocument.)
To find out which query would be faster usefully, you should try your actual XPath and LINQ to XML query on samples of your actual data. I would expect XPath to be faster in some situations, and LINQ to XML to be faster in others.
However, I'd be surprised if the query execution speed was actually the bottleneck in your code - do you have evidence that it is? You should first be asking yourself which is most readable. Implement that code, then see whether it's fast enough.
I'm using C# with .net 3.5 and have a few cases where I want to replace some substrings in the XML attributes of an XmlDocument with something else.
One case is to replace the single quote character with ' and the other is to clean up some files that contain valid XML but the attributes' values are no longer appropriate (say replace anything attribute which starts with "myMachine" with "newMachine").
Is there a simple way to do this, or do I need to go through each attribute of every node (recursively)?
One way to approach it is to select a list of the correct elements using Linq to XML, and then iterate over that list. Here's an example one-liner:
XDocument doc = XDocument.Load(path);
doc.XPathSelectElements("//element[#attribute-name = 'myMachine']").ToList().ForEach(x => x.SetAttributeValue("attribute-name", "newMachine"));
You could also do a more traditional iteration.
I suggest taking a look at LINQ to XML. There's a collection of code snippets that can help you get started here - LINQ To XML Tutorials with Examples
LINQ to XML should allow you to do what you're looking to do, and you'll probably find it easy once you've played with it a bit.
I have a web service which returns the following XML:
<Validacion>
<Es_Valido>NK7+22XrSgJout+ZeCq5IA==</Es_Valido>
</Validacion>
<Estatus>
<Estatus>dqrQ7VtQmNFXmXmWlZTL7A==</Estatus>
</Estatus>
<Generales>
<Nombre>V4wb2/tq9tEHW80tFkS3knO8i4yTpJzh7Jqi9MxpVVE=</Nombre>
<Apellido>jXyRpjDQvsnzZz+wsq6b42amyTg2np0wckLmQjQx1rCJc8d3dDg6toSdSX200eGi</Apellido>
<Ident_Clie>IYbofEiD+wOCJ+ujYTUxgsWJTnGfVU+jcQyhzgQralM=</Ident_Clie> <Fec_Creacion>hMI2YyE5h2JVp8CupWfjLy24W7LstxgmlGoDYjPev0r8TUf2Tav9MBmA2Xd9Pe8c</Fec_Creacion>
<Nom_Asoc>CF/KXngDNY+nT99n1ITBJJDb08/wdou3e9znoVaCU3dlTQi/6EmceDHUbvAAvxsKH9MUeLtbCIzqpJq74e QfpA==</Nom_Asoc>
<Fec_Defuncion />
</Generales>
The text inside the tags in encrypted, I need to decrypt the text, I've come up with a regular expressions solution but I don't think it's very optimal, is there a better way to do this? thanks!
I wouldn't use a regular expression. Load the XML with something like LINQ to XML, find every element which just has a text child, and replace the contents of that child with the decrypted form.
Do you know which elements will be encrypted? That would make it even easier. Basically you'll want something along the lines of:
// It's possible that modifying elements while executing Descendants()
// would be okay, but I'm not sure
List<XElement> elements = doc.Descendants().ToList();
foreach (XElement element in elements)
{
if (ShouldDecrypt(element)) // Whatever this would do
{
element.Value = Decrypt(element.Value);
}
}
(I'm assuming you know how to do the actual decryption part, of course.)
Never ever use regular expressions to parse XML. XmlReader and XmlDocument, both found inside System.Xml, provide a way better way to parse XML.
Do you know the type of encryption used? Look here to get the basics on the Cryptology capabilities in .NET
Is there a simple way to compare two XML structures to determine if they have the same structure and data?
I have a function that returns an XmlNode and I am trying to write unit tests for it. I store the correct XML result in a file. Durring the test I load the file into an XmlDocument, locate the proper XmlNode and compare against the result of the function. A straight compare does not work (as expected) and InnerXml does not work either.
I am considering removing all whitespace from InnerXml and comparing that, or writing my own compare to walk the tree, but I don't like either option much.
XNode.DeepEquals. Read the caveats before using it.
If you must use XmlDocument and its supporting types, consider using Microsoft's XmlDiffPatch, which performs customizable diff-operations on XML data structures.
Like CodeToGlory answered, XNode.DeepEquals() might fit your bill, check the remarks section on the MSDN page.
If you are stuck with XmlDocument (instead of XDocument), the answer is: No, there is no simple (existing way) to do it. XmlNode does not override Equals(), or provide an alternative. But it is not impossible to write, and that same Remarks section can be used as a starting point for a tree-walk algorithm.
Do get a clear picture of your requirements first, concerning Attributes, comments, CDATA nodes etc.