using System;
using System.Collections.Generic;
using System.Xml.Serialization;

public class Test
{
	public static void Main()
	{
		Document d = new Document();
		
		d.Placemarks = new List<Placemark>();
		
		d.Placemarks.Add(new Placemark("Mark" + d.Placemarks.Count, "What I am..."));
		d.Placemarks.Add(new Placemark("Mark" + d.Placemarks.Count, "What I am..."));
		d.Placemarks.Add(new Placemark("Mark" + d.Placemarks.Count, "What I am..."));
		
		d.Name = "Test.xml";
		
        XmlSerializer x = new XmlSerializer(typeof(Document));
		x.Serialize(System.Console.Out, d);
	}
}

public class Document
{
    [XmlElement("name")]
    public string Name { set; get; }

    [XmlElement("open")]
    public int Open { set; get; }

    //This will Serialize to a container <Placemarks>...</Placemarks>
    public List<Placemark> Placemarks { set; get; }
}

public class Placemark
{
    public Placemark() { }
    public Placemark(string name, string desc) 
    { 
        Name = name; 
        Description = desc; 
    }

    [XmlElement("name")]
    public string Name { set; get; }

    [XmlElement("description")]
    public string Description { set; get; }
}