Hi ilitirit, you could try this as a work-a-round:

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

[Serializable, XmlRoot("Message")]
public class Message
{
    private int _id;
    private string _description;

    [XmlAttribute("id")]
    public int Id
    {
        get { return _id; }
        set { _id = value; }
    }

    [XmlElement("Description")]
    public string Description
    {
        get { return _description; }
        set { _description = value; }
    }
}

[Serializable, XmlRoot("MessageList")]
public class MessageList : List<Message>, IXmlSerializable
{
    private int _id;
    private string _name = "";

    [XmlAttribute("id")]
    public int Id
    {
        get { return _id; }
        set { _id = value; }
    }

    [XmlElement("Name")]
    public string Name
    {
        get { return _name; }
        set { _name = value; }
    }

    #region IXmlSerializable Members

    public System.Xml.Schema.XmlSchema GetSchema()
    {
        throw new Exception("The method or operation is not implemented.");
    }

    public void ReadXml(XmlReader reader)
    {
        throw new Exception("The method or operation is not implemented.");
    }

    public void WriteXml(XmlWriter writer)
    {
        writer.WriteStartAttribute("MessageListId");
        writer.WriteValue(this.Id.ToString());
        writer.WriteEndAttribute();

        writer.WriteStartAttribute("MessageListName");
        writer.WriteValue(this.Name);
        writer.WriteEndAttribute();

        foreach (Message msg in this)
        {
            XmlSerializer serializer = new XmlSerializer(typeof(Message));
            serializer.Serialize(writer, msg);
        }
    }

    #endregion
}

public class Program
{
    public static void Main()
    {
        Program test = new Program();

        Message m1 = new Message();
        m1.Id = 1;
        m1.Description = "Message 1";

        Message m2 = new Message();
        m2.Id = 2;
        m2.Description = "Message 2";

        MessageList messageList = new MessageList();

        messageList.Add(m1);
        messageList.Add(m2);

        messageList.Id = 20070822;

        test.Serialize(messageList);

        Console.ReadLine();
    }

    private void Serialize<T>(T obj)
    {
        string xml;
        XmlSerializer serializer = new XmlSerializer(typeof(T));

        using (MemoryStream memoryStream = new MemoryStream())
        {
            using (XmlTextWriter xmlTextWriter = new XmlTextWriter(memoryStream,
Encoding.UTF8))
            {
                xmlTextWriter.Formatting = Formatting.Indented;

                serializer.Serialize(xmlTextWriter, obj);
                xml =
Encoding.UTF8.GetString(((MemoryStream)xmlTextWriter.BaseStream).ToArray()).Trim();
            }
        }

        Console.WriteLine(xml);
    }
}