I am trying to figure out how to write a regex that will strip out the values enclosed in an xml tag. For example,
string xml = "<MyElement1 attribute="bla"><MyElement1>12345</MyElement1></MyElement1>"
I want to know how to do the following:
match on MyElement1 nodes that do not have an attribute
So specifically, using my example I would match <MyElement1>12345</MyElement1> and replace <MyElement1> and </MyElement1> so that my final node looks like this: <MyElement1 attribute="bla">12345</MyElement1>
I've tried: [<][^>]*[>] but this matches on all elements. I'm not sure how to specify specific elements I want to match on.
I have made edits to make the question more focused and clearer as suggested based on the downvotes. I understand that I can use parse and navigate my document tree, but I prefer to use a regex replace of some sort because I want to apply this logic to any number of xml files with different tree structures, elements, and attributes.
Well you really don't need to use regular expressions, you just need to parse your XML using an XML parser.
One of the options you have would be to use the XDocument.Parse( xml ) method and XElement, where the first would be to parse the string, and the second to read it's tag and it's value. An example for reading it would be the following one
string xml = "<MyElement1>12345</MyElement1><MyElement2>abcd</MyElement2><MyElement3>12345</MyElement3><MyElement4>12345</MyElement4>";
// wrap your element in a rootnode (you seem to be missing one in your example)
var document = XDocument.Parse( $"<root>{xml}</root>");
// get the root node and loop over it's children (cast XNode to XElement in the process)
foreach (var node in document.Root.Nodes().OfType<XElement>()) {
// name is tag, value is well, it's value
Console.WriteLine($"{node.Name}: {node.Value}");
}
Note that for the example to parse the document correctly, you must add a rootnode, as xml can have only one rootnode in the document. In my sample, I enclosed the rootnode during the parsing
This sample code uses the System.Xml.Linq namespace, so don't forget to import that one.
One additional comment would be that your supplied XML code had an error in it (MyElemen4 opening tag with MyElement4 closing tag)
I would recommend using a XML Parser but if you want, you can use a simple regex like <([\w]*)>(.*?)<\/[\w]*>, this would return the name of the tag and the value inside.
Output:
Match 1
Full match 0-30 <MyElement1>12345</MyElement1>
Group 1. 1-11 MyElement1
Group 2. 12-17 12345
Match 2
Full match 30-59 <MyElement2>abcd</MyElement2>
Group 1. 31-41 MyElement2
Group 2. 42-46 abcd
Match 3
Full match 59-89 <MyElement3>12345</MyElement3>
Group 1. 60-70 MyElement3
Group 2. 71-76 12345
Match 4
Full match 89-118 <MyElemen4>12345</MyElement4>
Group 1. 90-99 MyElemen4
Group 2. 100-105 12345
Keep in mind it doesn't take in consideration of tag attributes. If you want to fetch a specific tag you can replace [\w] with the tag name you want.
Related
I am parsing a number of HTML documents, and within each need to try and extract a UK postal address. In order to do so I am parsing the HTML with AngleSharp and then looking for nodes with TextContent that match my RegEx:
var parser = new HtmlParser();
var source = "<html><head><title>Test Title</title></head><body><h1>Some example source</h1><p>This is a paragraph element and example postode EC1A 4NP</body></html>";
var document = parser.Parse(source);
Regex searchTerm = new Regex("([A-PR-UWYZ][A-HK-Y0-9][AEHMNPRTVXY0-9]?[ABEHMNPRVWXY0-9]? {1,2}[0-9][ABD-HJLN-UW-Z]{2}|GIR 0AA)");
var list = document.All.Where(m => searchTerm.IsMatch((m.TextContent ?? "").ToUpper()));
This returns 3 results, the html, body and p elements. The only element I want to return is the p element as that has the innerText matching the regex correctly. There may also be more than one match on a page so I can't just return the last result. I am looking to just return any elements where the text in that element (not in any child nodes) matches the regex.
Edit
I don't know in advance the doc structure or even the tag that the postcode will be within which is why I'm using regex. Once I have the result I am planning on traversing the dom to obtain the rest of the address so I don't just want to treat the doc as a string
If you are looking to extract a particular node within a well-formed HTML/XML document then have a look at utilising XPath. There's some examples here on MSDN
You can use utilities libraries such as HTML Tidy to "clean-up" the html and make it well formed if it isn't already.
Ok, I took a different approach in the end. I searched the HTML doc as a string with the RegEx NOT to parse the HTML but simply to find the exact match value. once I had that value it was simple enough to use an xpath expression to return the node. In the example above, the regex search returns EC1A 4NP and the following XPATH:
//*[contains(text(),'EC1A 4NP')]
returns the required node. For XPath ease, I switched from AngleSharp to HtmlAgilityPack for the HTML parsing
I've had a quick look at the doco of parser. Below is what you need to do if you want to check only the text in <p> tags.
var list = document.All.Where(m => m.LocalName.ToUpper() == "P" && searchTerm.IsMatch((m.TextContent ?? "").ToUpper()));
Hi guyes just had a quick question about using multi-line in regex:
The Regex:
string content = Regex.Match(onix.Substring(startIndex,endIndex - startIndex), #">(.+)<", RegexOptions.Multiline).Groups[1].Value;
Here is the string of text I am reading:
<Title>
<TitleType>01</TitleType>
<TitleText textcase="02">18th Century Embroidery Techniques</TitleText>
</Title>
Here is what I am getting:
01
What I want is everything between the
<Title> and </Title>.
This works perfectly when everything is on one line but since starts on another line it seems to be skipping it or not including it into the pattern.
Any assistance is much appreciated.
You must also use the Singleline option, along with Multiline:
string content = Regex.Match(onix.Substring(startIndex,endIndex - startIndex), #">(.+)<", RegexOptions.Multiline | RegexOptions.Singleline).Groups[1].Value;
But do yourself a favor and stop parsing XML using Regular Expressions! Use an XML parser instead!
You can parse the XML text using the XmlDocument class, and use XPath selectors to get to the element you're interested in:
XmlDocument doc = new XmlDocument();
doc.LoadXml(...); // your load the Xml text
XmlNode root = doc.SelectSingleNode("Title"); // this selects the <Title>..</Title> element
// modify the selector depending on your outer XML
Console.WriteLine(root.InnerXml); // displays the contents of the selected node
RegexOptions.Multiline will just change the meaning of ^ and $ to beginning/end of lines instead of beginning/end of the entire string.
You want to use RegexOptions.Singleline instead, which will result in . match line breaks (as well as everything else).
You might want to parse what is probably XML instead. If possible this is the preferred way of working instead of parsing it by employing regular expressions. Please disregard if not applicable.
I'm using C# in reading an XML file and counting how many "elements" there are in an XML tag, like this for example...
<Languages>English, Deutsche, Francais</Languages>
there are 3 "elements" inside the Languages tag: English, Deutsche, and Francais . I need to know how to count them and return the value of how much elements there are. The contents of the tag have the possibility of changing over time, because the XML file has to expand/accommodate additional languages (whenever needed).
IF this is not possible, please do suggest workarounds for the problem. Thank you.
EDIT: I haven't come up with the code to read the XML file, but I'm also interested in learning how to.
EDIT 2: revisions made to question
string xml = #"<Languages>English, Deutsche, Francais</Languages>";
var doc = XDocument.Parse(xml);
string languages = doc.Elements("Languages").FirstOrDefault().Value;
int count = languages.Split(',').Count();
In response to your edits which indicate that you're not simply trying to pull out comma separated strings from an XML element, then your approach to storing the XML in the first place is incorrect. As another poster commented, it should be:
<Languages>
<Language>English</Language>
<Language>Deutsche</Language>
<Language>Francais</Language>
</Languages>
Then, to get the count of languages:
string xml = #"<Languages>
<Language>English</Language>
<Language>Deutsche</Language>
<Language>Francais</Language>
</Languages>";
var doc = XDocument.Parse(xml);
int count = doc.Element("Languages").Elements().Count();
First, an "ideal" solution: do not put more than one piece of information in a single tag. Rather, put each language in its own tag, like this:
<Languages>
<Language>English</Language>
<Language>Deutsche</Language>
<Language>Francais</Language>
</Languages>
If this is not possible, retrieve the content of the tag with multiple languages, split using allLanguages.Split(',', ' '), and obtain the count by checking the length of the resultant array.
Ok, but just to be clear, an XML Element has a very specific meaning. In fact, the entire codeblock you have is an XML Element.
XElement xElm = new XElement("Languages", "English, Deutsche, Francais");
string[] elements = xElm.Value.Split(",".ToCharArray(), StringSplitOptions.RemoveEmptyEntries);
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.
How would you find the value of string that is repeated and the data between it using regexes? For example, take this piece of XML:
<tagName>Data between the tag</tagName>
What would be the correct regex to find these values? (Note that tagName could be anything).
I have found a way that works that involves finding all the tagNames that are inbetween a set of < > and then searching for the first instance of the tagName from the opening tag to the end of the string and then finding the closing </tagName> and working out the data from between them. However, this is extremely inefficient and complex. There must be an easier way!
EDIT: Please don't tell me to use XMLReader; I doubt I will ever use my custom class for reading XML, I am trying to learn the best way to do it (and the wrong ways) through attempting to make my own.
Thanks in advance.
You can use: <(\w+)>(.*?)<\/\1>
Group #1 is the tag, Group #2 is the content.
Using regular expressions to parse XML is a terrible error.
This is efficient (it doesn't parse the XML into a DOM) and simple enough:
string s = "<tagName>Data between the tag</tagName>";
using (XmlReader xr = XmlReader.Create(new StringReader(s)))
{
xr.Read();
Console.WriteLine(xr.ReadElementContentAsString());
}
Edit:
Since the actual goal here is to learn something by doing, and not to just get the job done, here's why using regular expressions doesn't work:
Consider this fairly trivial test case:
<a><b><a>text1<b>CDATA<![<a>text2</a>]]></b></a></b>text3</a>
There are two elements with a tag name of "a" in that XML. The first has one text-node child with a value of "text1", and the second has one text-node child with a value of "text3". Also, there's a "b" element that contains a string of text that looks like an "a" element but isn't because it's enclosed in a CDATA section.
You can't parse that with simple pattern-matching. Finding <a> and looking ahead to find </a> doesn't begin to do what you need. You have to put start tags on a stack as you find them, and pop them off the stack as you reach the matching end tag. You have to stop putting anything on the stack when you encounter the start of a CDATA section, and not start again until you encounter the end.
And that's without introducing whitespace, empty elements, attributes, processing instructions, comments, or Unicode into the problem.
You can use a backreference like \1 to refer to an earlier match:
#"<([^>]*)>(.*)</\1>"
The \1 will match what was captured by the first parenthesized group.
with Perl:
my $tagName = 'some tag';
my $i; # some line of XML
$i =~ /\<$tagName\>(.+)\<\/$tagname\>/;
where $1 is now filled with the data you captured
Going forward, if you get stuck check out regexlib.com
It's the first place I go when i get stuck on regex