using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using System.Xml;
using System.Xml.Linq;
public class MainClass {
    public static void Main() {

        XElement MyXElement = new XElement("Book"); 
        XComment MyxComment = new XComment("This is important message.");
        MyXElement.Add(MyxComment);
        Console.WriteLine(MyXElement);
    }
}