How to update XML file content with XDocument

Question

I have a XML file that contains this:

<?xml version="1.0" encoding="utf-8" ?> 
<TokenToCardMapping>
  <pair key ="2313123124122512" value="3412412512512512"/>
  <pair key ="3414125121259723" value="3749327923749723"/>
</TokenToCardMapping>

I am looking for way to add a new pair element to the TokenToCardMapping descendants with XDocument or XElement.

I have the key and value as strings and I just want to add a new pair.

if my new key and value are: 111111111111 , 222222222222 I want to update the xml to look like this:

<?xml version="1.0" encoding="utf-8" ?> 
<TokenToCardMapping>
  <pair key ="2313123124122512" value="3412412512512512"/>
  <pair key ="3414125121259723" value="3749327923749723"/>
  <pair key ="111111111111" value="222222222222"/>
</TokenToCardMapping>

Answer 1

It is easy with LINQ to XML

// create new element
var newElement = new XElement("pair",
                 new XAttribute("key","111111111111"
                 new XAttribute("value","222222222222"));

// load the XML Document
var xDoc = XDocument.Load("path");

// Add new element to the root element
xDoc.Root.Add(newElement);

//And save the XML file
xDoc.Save("path")

Note: You need to add a reference to System.Xml.Linq.dll from your project

And I would recommend you read the LINQ to XML tutorial for more details.