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Extract data from a XML string using linq vs xmlDocument

I have done the below many times using a xmlDocument approach, but I wanted to use the more powerful linq to xml approach.
However, I seem to have run into a wall.
I am getting data back from a restful API from twillio / crmText.
Here is a link to their site where their docs live:
http://crmtext.com/api/docs
Here is my XML string:
<response op="getcustomerinfo" status="200" message="ok" version="1.0">
<customer>
<totalMsg>3</totalMsg>
<custId>9008281</custId>
<custName></custName>
<timestamp>2015-04-30 16:17:19</timestamp>
<optinStatus>3</optinStatus>
<custMobile>6185551212</custMobile>
<subacct>1st Choice Courier</subacct>
</customer>
</response>
I need to find out the optinStatus. It should return 3.
I am using the below, which return the above xml
XDocument xdoc = XDocument.Parse(result1);
I have tried about 4000 different things, including:
IEnumerable<XElement> otinStatus = from el in xdoc.Elements("customer") select el;
IEnumerable<XElement> otinStatus2 = from el in xdoc.Elements("cusotmer.optinStatus") select el;
IEnumerable<XElement> otinStatus3 = from el in xdoc.Elements("optinStatus") select el;
All of which returns no results.
Please help, I know this is something simple I am missing.
Thank you in advance -- Joe

Retrieve an Element's Value
var status = xDoc
.Descendants("optinStatus") // get the optinStatus element
.Single() // we're expecting a single result
.Value; // get the XElement's value
Example
Here is a working Fiddle for you. You can see it running live here. The output is 3.
using System;
using System.Linq;
using System.Xml;
using System.Xml.Linq;
public class Program
{
public static void Main()
{
var xDoc = XDocument.Parse(xmlString);
var status = xDoc.Descendants("optinStatus").Single();
Console.WriteLine(status.Value);
}
private static string xmlString = #"
<response op=""getcustomerinfo"" status=""200"" message=""ok"" version=""1.0"">
<customer>
<totalMsg>3</totalMsg>
<custId>9008281</custId>
<custName></custName>
<timestamp>2015-04-30 16:17:19</timestamp>
<optinStatus>3</optinStatus>
<custMobile>6185312349</custMobile>
<subacct>1st Choice Courier</subacct>
</customer>
</response>
";
}
Explanation
Descendents() is an instance axes method (or just axes in shorthand). It returns an IEnumerable<XElement> of all matching descendents. On its results, we call Single(). It is a Linq method that returns the only element of a sequence. If there is more than one element, it throws an error. We're left with a single XElement. This represent an entire XML element. Since we only want its value not the entire element, we call the Value property. Bingo, we're done.
A Bit More Detail
Axes come in two kinds:
Instance axes methods, which MSDN lists here, are invokable members of the XElement, XDocument, and XNode classes.
Extension axes methods, which MSDN lists here, are invokable on collections.
With one exception, an axes method returns a collection of type IEnumerable<T>. The exception is Element(), which returns the first matching child object. That what AmatuerDev used and, as in your question, if you are only expecting a single result, it is a just as good if not better approach that is Descendants().
Retrieve an Attribute Value
Once we have an XElement, we can retrieve one of its attributes instead of its value. We do that by calling the Attributes() method. It returns the matching XAttribute. Since we only want the attribute value, we call the Value property. Voila.
// for attribute
var response = xDoc.Descendants("response").Single();
var attr = response.Attribute("status");
General Approach
Using Linq to XML is a two step process.
Call an axes method to obtain an IEnumerable<T> result.
Use Linq to query that.
See Also
Here is some relevant MSDN documentation:
How to: Retrieve the Value of an Element (LINQ to XML)
LINQ to XML Axes

Assuming xDoc being the XDocument. Have you tried..
var customer = xDoc.Root.Element("customer");
var optinStatus = customer.Element("optinStatus");
var optinStatusValue = optinStatus.Value;

Need to add xml element to last parent using linq c#

I'm really new to Linq and C# and I'm stuck on what is probably an obvious problem.
I have an existing XML file
<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<books>
<book>
<title>This is Title 1</title>
<author>John Doe</author>
<categories>
<category>How to</category>
<category>Technical</category>
</book>
<book>
<title>This is Title 2</title>
<author>Jane Brown</author>
<categories>
<category>Fantasy</category>
</categories>
</book>
</books>
I want to add a 2nd category to the second book in this file.
I've gotten this far:
var thiscat = doc.Root
.Element("book")
.Element("categories");
thiscat.Add(new XElement("category", "novel"));
But this adds a 3rd category to the first book. I need to learn how to point 'thiscat' at the last categories element rather than the first one. I've been sniffing around LastNode but haven't managed to get the syntax right.
This is my first question here. Please let me know if I'm not being clear or if I'm doing anything wrong.

Pete,
Here is an example that will search for the book by title This is Title 2 and add another category.
var elem = doc.Root.Elements("book").FirstOrDefault(x => x.Element("title").Value.Equals("This is Title 2"));
if (elem != null)
{
var category = elem.Element("categories");
category.Add(new XElement("category", "novel"));
}
Edit: More explanatoin.
First of we search the documents book elements for the matching title of This is Title 2 (effectively your second entry). By executing the FirstOrDefault extension method we either the get the first matching element (as XElement) or null.
Because we 'could' get a null value we must check if the value is null if not we move into the next step of locating the categories element. This can be done simply calling the elem.Element() method as we only expect one element.
Finally we add a new XElement to the category element.
Hope this helps.
Cheers.

To answer your question quite literally, you could modify the statement as follows:
var thiscat = doc.Root
.Elements("book")
.Skip(1)
.First()
.Element("categories");
The "Element" function returns the first element of that type found. In this case, we used "Elements" instead to return an IEnumerable containing all of the elements named "book", and then we used the LINQ "skip" function to skip the first (returning another IEnumerable of all the remaining elements), and then we took just the first element in the IEnumerable (back to a single XElement).
Another way you could have gotten to the answer is as follows:
var thiscat = doc.Root
.Element("book")
.ElementsAfterSelf()
.First()
.Element("categories");
ElementsAfterSelf returns an IEnumerable of all the sibling elements after the calling object.
LINQ is a really critical part of programming in C# and it's good to see you're trying to learn it from the beginning. Although your methodology here in adding a specific element to a specific place programmatically is questionable (obviously it is a contrived example), in playing around like this you will probably learn a bit about LINQ and that is always good.

First you should get your second book element.According to your code:
var thiscat = doc.Root
.Element("book")
.Element("categories");
This statement returns just one categories element which belongs to your first book.Because you are using Element instead of Elements. Let's go step by step.
A proper way to get second element is using Descendants like this:
var secondBook = doc.Descendants("book")[1];
Descendants returning a collection of your books.And we are getting second element with indexer.Now we need to select your categories element under the book element.
var categories = secondBook.Element("categories");
Now we have our categories element and we can add our new category and save Xml Document:
categories.Add(new XElement("category", "novel"));
doc.Save(path);
And that's all.If you understand that logic you can modify your html file however you like.Besides you can make all of these in one line:
doc.Descendants("book")[1]
.Element("categories")
.Add(new XElement("category", "novel"));

This should work( slightly lengthy solution as it helps understand the fundamentals better):
XmlElement rootNode = xd.DocumentElement; //gives <books> the root node
XmlNodeList cnodes= rootNode.ChildNodes; //gets the childnodes of <books>
XmlNode secondBook= cnodes.Item(1); //second child of <books> i.e., the <book> you want
XmlNodeList bnodes= secondBook.ChildNodes; //gets the childnodes of that <book>
XmlNode categories= bnodes.Item(2); //gets the third child i.e.,<categories>
//making the new <category> node
string xmlContent = "<category>novel</category>";
XmlDocument doc = new XmlDocument();
doc.LoadXml(xmlContent);
XmlNode newNode = doc.DocumentElement;
//making the new node completes
categories.AppendChild(newNode); //append the new node to <categories> as a child

How do you sort an XDocument parent node based its child?

In C# I am trying to sort an XDocument using OrderByDescending. The goal is to read one of the child nodes which contains a date/time stamp and reorder the parent nodes.
I load the XML from a saved file like this:
XDocument Doc = new XDocument();
Doc= XDocument.Load(filename);
Here is an example of my XML:
<KS>
<Team>
<TeamName>Knights</TeamName>
<TeamColor>blue</TeamColor>
<LastAccessed>5/9/2013 2:34:22 PM</LastAccessed>
</Team>
<Team>
<TeamName>Rangers</TeamName>
<TeamColor>red</TeamColor>
<LastAccessed>5/9/2013 3:49:06 PM</LastAccessed>
</Team>
<Team>
<TeamName>Eagles</TeamName>
<TeamColor>green</TeamColor>
<LastAccessed>5/9/2013 3:50:18 PM</LastAccessed>
</Team>
</KS>
I would like to reorder <Team> descending based on the child element <LastAccessed>.
I have tried the following without any luck:
var results = Doc.Root.Descendants("Team").OrderByDescending(p => p.Element("LastAccessed"));
XDocument node = new XDocument(Doc.Descendants("KS").OrderByDescending(x => x.Element("Team").Element("LastAccessed").Value.Trim()));
Any suggestions how one would sort XML parent nodes based on a value stored in the child node?

You should have gotten an error that said:
At least one object must implement IComparable.
Please always include these errors in your questions.
You need to provide a child of the Team element that supports the IComparable interface. You need to get the value rather than the XElement that .Elements gives you.
Change your results line to the below and it will work.
var results = Doc.Descendants("Team").OrderByDescending(p => DateTime.Parse(p.Element("LastAccessed").Value));

var results = Doc.Root.Descendants("Team").OrderByDescending(p => (DateTime)p.Element("LastAccessed"));

Check all the children for XElement

I have XElement object which is my XML tree read from XML file. Now I want to check all the nodes in this tree to get first attribute name and value. Is there any simple way to go through all of the nodes (from root till leaves)? My XML file has got very many different and strange nodes - that's why it's harder to solve this issue. I thought about writing some recursion, but hope it's another way to solve that easier.

Maybe take a look to Xpath. an XPath like this //*[#id=42] could do the job.
It means get all nodes which have an attribute "id" of value 42.
You can do just //* which gonna returns all nodes in a tree.
Xpath :
http://msdn.microsoft.com/en-gb/library/ms950786.aspx
Syntax :
http://msdn.microsoft.com/en-us/library/ms256471.aspx

You can get all children elements using XElement.Elements().
Here's some code using recursion to get all elements of each level:
void GetElements(XElement element){
var elements = element.Elements();
foreach(Element e in elements){
//some stuff here
if(e.Elements() != null)
GetElements(e);
}
}

Add elements to XDocument after LINQ Query

I have the following XML LINQ query from my XDocument.
var totals = (from x in MyDocument.Descendants("TOTALS") select x).FirstOrDefault();
Once I have found my totals node I need to add some elements to that node and push that change to the XDocument.

So just make the change to the returned node... unless you clone it, it will still be part of the document.
Btw, your query expression isn't adding anything - simpler code would be:
var totals = MyDocument.Descendants("TOTALS").FirstOrDefault();

you can use AddAfterSelf() to add new nodes against totals. Those changes will automatically get attached to the main XDocument, since totals is referencing an XElement inside the document.

totals.Add(new XElement("NewNode", "New node value"));