XML / XSL

using System;
using System.Xml;
using System.Xml.Schema;
namespace a
{
   class Program
   {
      static public void vvv(Object sender, ValidationEventArgs e)
      {
         Console.WriteLine(e.Message);
         throw new XmlSchemaValidationException();
      }

      static void Main(string[] args)
      {
         try
         {
            XmlDocument xmldoc = new XmlDocument();
            xmldoc.PreserveWhitespace = false;

            xmldoc.Load("Changes.xml");
            Console.WriteLine(xmldoc.DocumentElement.Name);
            Console.WriteLine("The document has {0} entities", xmldoc.DocumentType.Entities.Count);

            XmlSchemaSet schema = new XmlSchemaSet();
            schema.Add("", "change-history.xsd");
            xmldoc.Schemas = schema;
            xmldoc.Validate(vvv);
            Console.WriteLine("Document validated!");
         }
         catch (XmlSchemaValidationException)
         {
            Console.WriteLine("Document didn't validate!");
         }
      }
   }
}

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="unqualified" attributeFormDefault="unqualified">
  <xs:element name="change-history">
    <xs:annotation>
      <xs:documentation>Comment describing your root element</xs:documentation>
    </xs:annotation>
    <xs:complexType>
      <xs:sequence>
        <xs:element name="items">
          <xs:complexType>
            <xs:sequence maxOccurs="unbounded">
              <xs:element name="item">
                <xs:complexType>
                  <xs:sequence maxOccurs="unbounded">
                    <xs:element name="version">
                      <xs:complexType>
                        <xs:sequence maxOccurs="unbounded">
                          <xs:element name="change">
                            <xs:complexType>
                              <xs:simpleContent>
                                <xs:extension base="xs:string">
                                  <xs:attribute name="reason" type="xs:string" use="optional"/>
                                </xs:extension>
                              </xs:simpleContent>
                            </xs:complexType>
                          </xs:element>
                        </xs:sequence>
                        <xs:attribute name="number" type="xs:string" use="required"/>
                      </xs:complexType>
                    </xs:element>
                  </xs:sequence>
                  <xs:attribute name="name" type="xs:string" use="required"/>
                </xs:complexType>
              </xs:element>
            </xs:sequence>
          </xs:complexType>
        </xs:element>
      </xs:sequence>
      <xs:attribute name="product" type="xs:string" use="required"/>
    </xs:complexType>
  </xs:element>
</xs:schema>

<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE change-history [
<!ENTITY eacute "&#xE9;">
]>
<change-history product="Sample" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="change-history.xsd">
   <items>
      <item name="Sample.exe">
         <version number="2.21.0">
            <change reason="issue 11">Added license to executable.</change>
            <change>&eacute;Fixed bug in executable.</change>
         </version>
      </item>
   </items>
</change-history>

xquery version "1.0";
declare function local:valid-email($email as xs:string)
	  as xs:boolean
{
	matches($email, '[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}')
};

class Program
    {
        class Sample
        {
            public Sample()
            {
                string xmlString = "<xml><item>a<!--Item A--></item><item>b<!--Item B--></item><item>b<!--Item C--></item></xml>";

                XmlDocument document = new XmlDocument();
                document.LoadXml(xmlString);

                //Navigate throgh all the nodes and check if a node is a comment
                Console.WriteLine("Method 1");

                XmlNodeList nodes = document.SelectNodes("xml/item");

                foreach (XmlNode childnode in nodes)
                {
                    if (childnode.LastChild.NodeType == XmlNodeType.Comment)
                    {
                        Console.WriteLine(childnode.LastChild.InnerText);
                    }
                }

                //Using Exact XQuery
                Console.WriteLine("\n\nMethod 2");
                
                nodes = document.SelectNodes("xml/item/comment()");

                foreach (XmlNode childnode in nodes)
                {   
                    Console.WriteLine(childnode.InnerText);                    
                }
            }
        }

        static void Main(string[] args)
        {
            Sample sample = new Sample();
            Console.ReadLine();
        }
}