Develop Reference

xpath to return value from xml doc

I'm wondering if there is a way to do the following with one xpath expression:
I have an XML doc similar to this but with many 'results',
<result>
<id>1</id>
<name>joe</name>
</result>
<result>
<id>2</id>
<name>jim</name>
</result>
I'm passing a variable into a C# utility along with the xml, and want to return the name where the id = the variable.
I could loop through the xml until reach what I'm after but if there's a handy xpath way to do it I'm listening...
thanks

Assuming you have a root element in there like "results" that XPath can validate, and that you don't have any other nodes named "result"...
//result[id=1]/name
Or you could get the text outright, instead of it being returned in a node
//result[id=1]/name/text()
And if you want to make sure that there's only one result, you could surround it with parens and put a [1] after
(//result[id=1]/name/text())[1]
I would also recommend testing with one of the xpath test sites out there like this one, but beware that different xpath/xml parsers sometimes behave differently.

Searching XML Elements by Attributes (C#)

I'm Trying to check XML elements for specific attributes so I can keep from saving duplicate element entries. the XML looks more or less like this:
<root>
<artist name="Coldplay">
<track name="yellow" artist="Coldplay" url="coldplay.com/yellow" playCount="123" />
<track name="fix you" artist="Coldplay" url="coldplay.com/fixyou" playCount="135" >
</artist>
//ect.
</root>
google and various search results suggest something like
[#id='foo']
but i don't know what that is and for reasons that might be more obvious to you than to me i can't "google" a collection of special characters like that without getting bizarre results. So If anyone can offer a suggestion for an if checking statement I'd be much obliged! or a name or link for how special characters are used in C#.

It's an XPath expression. You can use them along with a variety of XML-related objects in c#.
XmlDocument xd = new XmlDocument();
xd.LoadXml( xmlString );
XmlNodeList nodes = xd.SelectNodes( "//root/artist/track[#name='yellow']" );
General Reference: http://msdn.microsoft.com/en-us/library/ms256086.aspx
XPath with LINQ: http://msdn.microsoft.com/en-us/library/bb675183.aspx.

That's an XPath expression - but personally, I'd use LINQ to XML for the searching myself:
XDocument doc = XDocument.Load("test.xml");
var track = doc.Descendants("track")
.Where(t => (string) t.Attribute("id") == "foo")
.FirstOrDefault();
(Use Single, SingleOrDefault, First etc if you want to.)

xpath return string instead of nodelist

I am working on a biztalk project and I need to copy (filtered) content from 1 xml to another.
I have to do this with xpath, I can't use xsl transformation.
So my xpath to get the content from the source xml file is this:
//*[not(ancestor-or-self::IN1_Insurance)]|//IN1_Insurance[2]/descendant-or-self::*
Now this returns an xmlNodelist. Is it possible to return a string with all the nodes in it like:
"<root><node>text</node></root>"
If I put string() before my xpath it returns the values, but I want the whole xml in a string (with nodes..), so I could load that string in another xmldocument. I think this is the best method for my problem.
I know I can loop over the xmlnodelist and append the nodes to the new xmldocument, but it's a bit tricky to loop in a biztalk orchestration and I want to avoid this.
The code I can use is C#.
I've tried to just assign the nodelist to the xmldocument, but this throws a cast error (obvious..).
The way I see it is that I have 2 solutions:
assign the nodelist to the xmldocument without a loop (not possible i think in C#)
somehow convert the nodelist to string and load this in the xmldocument
load the xpath directly in the new xmldocument (don't know if this is possible since it returns a nodelist)
Thanks for your help
edit:
sample input:
<root>
<Patient>
<PatientId></PatientId>
<name></name>
</Patient>
<insurance>
<id>1</id>
<billing></billing>
</insurance
<insurance>
<id>2</id>
<billing></billing>
</insurance>
<insurance>
<id>3</id>
<billing></billing>
</insurance>
</root>
Now I want to copy this sample to another xmldocument, but without insurance node 2 and 3 (this is dynamically, so it could be unsurance node 1 and 2 to delete, or 1 and 3...)
So this has to be the output:
<root>
<Patient>
<PatientId></PatientId>
<name></name>
</Patient>
<insurance>
<id>1</id>
<billing></billing>
</insurance>
</root>
What I am doing now is use the xpath to get the nodes I want. Then I want to assign the result to the new xmldocument, but this is not possible since I get the castException
string xpath = "//*[not(ancestor-or-self::IN1_Insurance)]|//IN1_Insurance[2]/descendant-or-self::*";
xmlDoc = new System.Xml.XmlDocument();
xmlDoc = xpath(sourceXml, strXpath); <= cast error (cannot cast xmlnodelist to xmldocuemnt)
I know the syntax is a bit strange, but it is biztalk c# code..

The most straightforward solution would indeed be to "loop over the xmlnodelist and append (import) the nodes to the new xmldocument", but since you can't loop, what other basic things can/can't you do?
To serialize the nodelist, you could try using XmlNodeList.toString(). If that worked, you'd get a strange beast, because it could be duplicating parts of the XML document several times over. Especially since you're explicitly including ancestors and descendants directly in the nodelist. It would not be something that you could parse back in and have a result that resembled the nodelist you started with.
In other words, it would be best to loop over the XmlNodeList and import the nodes to the new XmlDocument.
But even so, I would be really surprised if you wanted to put all these ancestor and descendant nodes:
//*[not(ancestor-or-self::IN1_Insurance)]|//IN1_Insurance[2]/descendant-or-self::
directly into the new XML document. If you post some sample input and the desired output, we can probably help determine if that's the case.
Update:
I see what you're trying to do: copy an XML document, omitting all <insurance> elements (and their descendants) except the one you want.
This can be done without a loop if the output is as simple as your sample output: only one <Patient> and one <insurance> element, with their descendants, under one top-level element.
Something like (I can't test this as I don't have a biztalk server):
string xpathPatient = "/*/Patient";
string xpathInsuran = "/*/insurance[id = " + insId + "]"; // insId is a parameter
xmlDoc = new System.Xml.XmlDocument();
xmlPatient = xpath(sourceXml, xpathPatient);
xmlInsuran = xpath(sourceXml, xpathInsuran);
XmlElement rootNode = xmlDoc.CreateElement("root");
xmlDoc.AppendChild(rootNode);
//**Update: use [0] to get an XmlNode from the returned XmlNodeList (presumably)
rootNode.AppendChild(xmlDoc.ImportNode(xmlPatient[0], true));
rootNode.AppendChild(xmlDoc.ImportNode(xmlInsuran[0], true));
I confess though, I'm curious why you can't use XSLT. You're approaching tasks that would be more easily done in XSLT than in XPath + C# XmlDocument.
Update: since the xpath() function probably returns an XmlNodeList rather than an XmlNode, I added [0] to the first argument to ImportNode() above. Thanks to #Martin Honnen for alerting me to that.

XPath is a query language (only) for XML documents.
It operates on an abstract model -- the XML INFOSET, and cannot either modify the structure of the XML document(s) it operates on or serialize the INFOSET information items back to XML.
Therefore, the only way to achieve such serialization is to use the language that is hosting XPath.
Apart from this, there are obvious problems with yout question, for example these is no element named IN1_Insurance in the provided XML document -- therefore the XPath expression provided:
//*[not(ancestor-or-self::IN1_Insurance)]|//IN1_Insurance[2]/descendant-or-self::*
selects all elements in the document.
Note:
The described task is elementary to fulfil using XSLT.
Finally: If you are allowed to use C# then you can use the XslCompiledTransform (or XslTransform) class. Use its Transform() method to carry out the following transformation against the XML document:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:template match="node()|#*">
<xsl:copy>
<xsl:apply-templates select="node()|#*"/>
</xsl:copy>
</xsl:template>
<xsl:template match="insurance[not(id=1)]"/>
</xsl:stylesheet>
This produces exactly the wanted result:
<root>
<Patient>
<PatientId></PatientId>
<name></name>
</Patient>
<insurance>
<id>1</id>
<billing></billing>
</insurance>
</root>

XmlDocument SelectSingleNode of improperly formed XML

I have a XmlDocument which is not properly formed
<library>
<dept>
<books></books>
<language></language>
</dept>
<dept>
<lecturer></lecturer>
</dept>
</library>
I want to do a XmlDocument.SelectSingleNode for 'lecturer' tag.
When I select ChildNodes of <library> tag, I get only <books> and <language> but not <lecturer>.
How do I get XmlNode object of tag?

The XML is well formed XML. It would not load into a XmlDocument otherwise.
The only ChildNodes of library are dept nodes.
To get lecturer, you can do the following:
XmlDocument.SelectSingleNode("library/dept/lecturer");

To parse csproj file, use GetElementsByTagName(). I dont know why SelectSingleNode() is not working!
Thank you
Sid

Using C# Regular expression to replace XML element content

I'm writing some code that handles logging xml data and I would like to be able to replace the content of certain elements (eg passwords) in the document. I'd rather not serialize and parse the document as my code will be handling a variety of schemas.
Sample input documents:
doc #1:
<user>
<userid>jsmith</userid>
<password>myPword</password>
</user>
doc #2:
<secinfo>
<ns:username>jsmith</ns:username>
<ns:password>myPword</ns:password>
</secinfo>
What I'd like my output to be:
output doc #1:
<user>
<userid>jsmith</userid>
<password>XXXXX</password>
</user>
output doc #2:
<secinfo>
<ns:username>jsmith</ns:username>
<ns:password>XXXXX</ns:password>
</secinfo>
Since the documents I'll be processing could have a variety of schemas, I was hoping to come up with a nice generic regular expression solution that could find elements with password in them and mask the content accordingly.
Can I solve this using regular expressions and C# or is there a more efficient way?

This problem is best solved with XSLT:
<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="#* | node()">
<xsl:copy>
<xsl:apply-templates select="#* | node()"/>
</xsl:copy>
</xsl:template>
<xsl:template match="//password">
<xsl:copy>
<xsl:text>XXXXX</xsl:text>
</xsl:copy>
</xsl:template>
</xsl:stylesheet>
This will work for both inputs as long as you handle the namespaces properly.
Edit : Clarification of what I mean by "handle namespaces properly"
Make sure your source document that has the ns name prefix has as namespace defined for the document like so:
<?xml version="1.0" encoding="utf-8"?>
<secinfo xmlns:ns="urn:foo">
<ns:username>jsmith</ns:username>
<ns:password>XXXXX</ns:password>
</secinfo>

I'd say you're better off parsing the content with a .NET XmlDocument object and finding password elements using XPath, then changing their innerXML properties. It has the advantage of being more correct (since XML isn't regular in the first place), and it's conceptually easy to understand.

From experience with systems that try to parse and/or modify XML without proper parsers, let me say: DON'T DO IT. Use an XML parser (There are other answers here that have ways to do that quickly and easily).
Using non-xml methods to parse and/or modify an XML stream will ALWAYS lead you to pain at some point in the future. I know, because I have felt that pain.
I know that it seems like it would be quicker-at-runtime/simpler-to-code/easier-to-understand/whatever if you use the regex solution. But you're just going to make someone's life miserable later.

You can use regular expressions if you know enough about what you are trying to match. For example if you are looking for any tag that has the word "password" in it with no inner tags this regex expression would work:
(<([^>]*?password[^>]*?)>)([^<]*?)(<\/\2>)
You could use the same C# replace statement in zowat's answer as well but for the replace string you would want to use "$1XXXXX$4" instead.

Regex is the wrong approach for this, I've seen it go so badly wrong when you least expect it.
XDocument is way more fun anyway:
XDocument doc = XDocument.Parse(#"
<user>
<userid>jsmith</userid>
<password>password</password>
</user>");
doc.Element("user").Element("password").Value = "XXXX";
// Temp namespace just for the purposes of the example -
XDocument doc2 = XDocument.Parse(#"
<secinfo xmlns:ns='http://tempuru.org/users'>
<ns:userid>jsmith</ns:userid>
<ns:password>password</ns:password>
</secinfo>");
doc2.Element("secinfo").Element("{http://tempuru.org/users}password").Value = "XXXXX";

Here is what I came up with when I went with XMLDocument, it may not be as slick as XSLT, but should be generic enough to handle a variety of documents:
//input is a String with some valid XML
XmlDocument doc = new XmlDocument();
doc.LoadXml(input);
XmlNodeList nodeList = doc.SelectNodes("//*");
foreach (XmlNode node in nodeList)
{
if (node.Name.ToUpper().Contains("PASSWORD"))
{
node.InnerText = "XXXX";
}
else if (node.Attributes.Count > 0)
{
foreach (XmlAttribute a in node.Attributes)
{
if (a.LocalName.ToUpper().Contains("PASSWORD"))
{
a.InnerText = "XXXXX";
}
}
}
}

The main reason that XSLT exist is to be able to transform XML-structures, this means that an XSLT is a type of stylesheet that can be used to alter the order of elements och change content of elements. Therefore this is a typical situation where it´s highly recommended to use XSLT instead of parsing as Andrew Hare said in a previous post.