C#:
Working with XML

using System;
using System.Xml;
using System.Xml.Linq;

class Program
{
     static void Main()
     {
        var xmlString = @"<bookstore>
                            <book>
                              <title lang=""en"">Head First C#</title>
                              <price>39.99</price>
                            </book>
                          </bookstore>";

        // Parse the string into an XDocument
        XDocument doc = XDocument.Parse(xmlString);

        // Add a new book
        doc.Element("bookstore").Add(
            new XElement("book",
                new XElement("title", "Learning XML", new XAttribute("lang", "en")),
                new XElement("price", 29.99)
            )
        );

        // Write the XML to console
        Console.WriteLine(doc);

        // Load the document
        XmlDocument xmlDoc = new XmlDocument();
        xmlDoc.LoadXml(xmlString);

        // Retrieve all prices
        XmlNodeList prices = xmlDoc.GetElementsByTagName("price");
        foreach (XmlNode price in prices)
        {
            Console.WriteLine(price.InnerText);
        }
     }
}

// Sample Output:
// <bookstore>
//  <book>
//    <title lang="en">Head First C#</title>
//    <price>39.99</price>
//  </book>
//  <book>
//    <title lang="en">Learning XML</title>
//    <price>29.99</price>
//  </book>
// </bookstore>
// 39.99
// 29.99