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C# XElement Get Attribute with a Namespace

I have a number of XElements, but their "href" attribute has a namespace. When I try to get it, it returns null.
<link xlink:href="The/href" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="a/location">A value</link>
I have tried:
XElement linkEl = doc.Root.Element("link");
string hrefValue = linkEl.Attribute("href").Value //null;
I have also tried adding the namespace to the "href" like "xlink:href" in Attribute(), but this results in an error. Anyone know how to perform this magic?

Try this one:
XDocument doc = XDocument.Parse(#"<link xlink:href=""The/href"" xmlns:xlink=""http://www.w3.org/1999/xlink"" xmlns=""a/location"">A value</link>");
XNamespace ab = "http://www.w3.org/1999/xlink";
string hrefValue = doc.Root.Attribute(ab + "href").Value;

For your sample xml you can't find your element by using its Name it must be the LocalName of the element.
To get element by LocalName here is the sample:
var linkElement = doc.Root.Elements().Where(e => e.Name.LocalName == "link").FirstOrDefault();
var linkAttribute = linkElement.Attributes().Where(a => a.Name.LocalName == "href").FirstOrDefault();
var hrefValue = linkAttribute.Value;

Xdocument parse file and read values

I have the below sample XML , I need to retrive the values for the following two fields txJu and ddate.I also have the code but it is giving null expection
<Doc id="580171" ddate="2019-06-21" >
<ref dtRef="2019-08-21">
<dr>
<cr>
<pj>
<pr>
<dDup txJu="0.00" txFi="0.00" txcOp="0.00" />
<comp txJu="12.96" txFi="2.45" txOp="0.00" />
</pr>
</pj>
</cr>
</dr>
</ref>
</Doc>
var xdoc = XDocument.Load(file);
string txJu = xdoc.Root.Element("comp").Attribute("txJu").Value;
string ddate = xdoc.Root.Element("Doc").Attribute("ddate").Value;

There are a couple of issues with your code. Your Root element doesn't contain comp node, Doc element is root itself, string ddate = string value = ... is invalid C# declaration.
You can modify your code per following
var compElement = xdoc.Root?.DescendantsAndSelf("comp").FirstOrDefault();
string txJu = compElement?.Attribute("txJu")?.Value;
string ddate = xdoc.Root?.Attribute("ddate")?.Value;
string value = ddate;
Use DescendantsAndSelf method to get a collection of filtered comp elements and use first of them. Access ddate attribute directly in Root element. Use null-conditional operator ? to avoid possible null reference exceptions

LINQ xml finding nodes returns null

I try to parse an xml file with XDocument class, with criteria that if the child node matches a given string, its parent node is selected.
<SalesQuotes xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://api.some.com/version/1">
<Pagination>
<NumberOfItems>2380</NumberOfItems>
<PageSize>200</PageSize>
<PageNumber>1</PageNumber>
<NumberOfPages>12</NumberOfPages>
</Pagination>
<SalesQuote>
<Guid>825634b9-28f5-4aa7-98e7-5e4a4ed6bc6a</Guid>
<LastModifiedOn>2018-01-09T12:23:56.6133445</LastModifiedOn>
<Comments>Please note:
installation is not included in this quote
</Comments>
</SalesQuote>
</SalesQuotes>
I tried using
var contents = File.ReadAllText(path: "test1.xml");
var doc = XDocument.Parse(contents);
var root = doc.Root;
var sq = root.Elements("SalesQuote");//return null
var theQuote = root.Elements("SalesQuote").Where(el => el.Element("Guid").Value == "825634b9-28f5-4aa7-98e7-5e4a4ed6bc6a");//return null
var theAlternativeQuote =
from el in doc.Descendants("SalesQuote").Elements("Guid")
where el.Value == "825634b9-28f5-4aa7-98e7-5e4a4ed6bc6a"
select el;//return null
I can't seem to find what's wrong.
Any help is much appreciated! Thanks.

You ignored the namespace bro.
Do remove the xmlns attribute in your XML or try this:
var contents = File.ReadAllText("XMLFile1.xml");
var doc = XDocument.Parse(contents);
var root = doc.Root;
XNamespace ns = "http://api.some.com/version/1";
var sq = root.Descendants(ns + "SalesQuotes"); //return null
var theQuote = root.Elements(ns + "SalesQuote")
.Where(el => el.Element(ns + "Guid").Value == "825634b9-28f5-4aa7-98e7-5e4a4ed6bc6a"); //return null
var theAlternativeQuote =
from el in doc.Descendants(ns + "SalesQuote").Elements(ns + "Guid")
where el.Value == "825634b9-28f5-4aa7-98e7-5e4a4ed6bc6a"
select el; //return null

If you are not too concerned about keeping your current implementation, you could consider using a Typed DataSet and load your XML into fully typed, structured objects.
Querying those objects with Linq will be more straight forward than what I see in your current implementation.
You might also find this useful:
SO Question: Deserialize XML Document to Objects

yap, you're missing the namespace that you can grab with document.Root.GetDefaultNamespace()
// Load
var document = XDocument.Parse(xml);
var xmlns = document.Root.GetDefaultNamespace();
// Find
var query = from element in document
.Descendants(xmlns + "SalesQuote")
.Elements(xmlns + "Guid")
where element.Value == "825634b9-28f5-4aa7-98e7-5e4a4ed6bc6a"
select element;

get xml node value from xml string

I have xml which contain xml namespace. i need to get value from its xml node
<personxml:person xmlns:personxml="http://www.your.example.com/xml/person" xmlns:cityxml="http://www.my.example.com/xml/cities">
<personxml:name>Rob</personxml:name>
<personxml:age>37</personxml:age>
<cityxml:homecity>
<cityxml:name>London</cityxml:name>
<cityxml:lat>123.000</cityxml:lat>
<cityxml:long>0.00</cityxml:long>
</cityxml:homecity>
Now i want to get value of tag <cityxml:lat> as 123.00
Code :
string xml = "<personxml:person xmlns:personxml='http://www.your.example.com/xml/person' xmlns:cityxml='http://www.my.example.com/xml/cities'><personxml:name>Rob</personxml:name><personxml:age>37</personxml:age><cityxml:homecity><cityxml:name>London</cityxml:name><cityxml:lat>123.000</cityxml:lat><cityxml:long>0.00</cityxml:long></cityxml:homecity></personxml:person>";
var elem = XElement.Parse(xml);
var value = elem.Element("OTA_personxml/cityxml:homecity").Value;
Error i am getting
The '/' character, hexadecimal value 0x2F, cannot be included in a name.

You need to use XNamespace. For example:
XNamespace ns1 = "http://www.your.example.com/xml/person";
XNamespace ns2 = "http://www.my.example.com/xml/cities";
var elem = XElement.Parse(xml);
var value = elem.Element(ns2 + "homecity").Element(ns2 + "name").Value;
//value = "London"
Create XNamespace using a string that contains the URI, then combine the namespace with the local name.
For more information, see here.

You are better off using a XmlDocument to navigate your xml.
XmlDocument doc = new XmlDocument();
doc.LoadXml(xml);
XmlNode node = doc.SelectSingleNode("//cityxml:homecity/cityxml:lat");
string latvalue = null;
if (node != null) latvalue = node.InnerText;

The error I got with your code was that there needs to be a namespace to parse the XML properly
Try :
XNamespace ns1 = "http://www.your.example.com/xml/cities";
string value = elem.Element(ns1 + "homecity").Element(ns1 + "name").Value;
I would still advice using XDocuments to parse if possible, but the above is fine if your way is a must.

Getting decendant node that contains ":"?

I have loaded a XML into a XDocument that looks something like this :
<MyXML xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.datacontract.org/2004/07/MyApp.Client.Main.GUI.Report">
<Wrapper xmlns:d2p1="http://schemas.datacontract.org/2004/07/MyApp.Business.Entity">
<d2p1:_MultipelAttributId>156</d2p1:_MultipelAttributId>
</Wrapper>
</MyXML>
Now I need to get the value of _MultipelAttributId but when stating this :
XElement element = (from cml2 in doc.Descendants("d2p1:_MultipelAttributId") select cml2).FirstOrDefault();
I get exception about the ":"?
So how do I get the valiue?

XNamespace ns = "http://schemas.datacontract.org/2004/07/MyApp.Business.Entity";
var element = xDoc.Descendants(ns + "_MultipelAttributId").FirstOrDefault();

The element name you're querying is not correct. Try this:
XElement element = (
from cml2 in doc.Descendants()
where cml2.Name.LocalName == "_MultipelAttributId"
select cml2).FirstOrDefault();

This MSDN article explains well how to work with namespaces in Linq to XML
http://msdn.microsoft.com/en-us/library/bb669152.aspx
XNamespace d2p1 = "http://schemas.datacontract.org/2004/07/MyApp.Business.Entity";
XElement multipelAttributId = doc.Descendants(d2p1 + "_MultipelAttributId").FirstOrDefault();
Notice that you can seamly create an XNamespace or an XName from a string because Microsoft have writen inplicit casts for these types.