using System;

using System.IO;

using System.Xml;

using System.Xml.Linq;

using System.Xml.Schema;

using System.Xml.Serialization;

public class Program

{

    public static void Main()

    {

        var result = new Result() 

        {

            FOO = new ElementsWrapper {

                Elements = new XElement[] {

                    new XElement( "BAR", "Hello World"),

                    new XElement( "BAR2", "Hello World"),

                    new XElement( "BAR3", "Hello World"),

                }

            },

            Message = "Hello World"

        };

        Console.WriteLine(result);

    }

    [XmlRoot(ElementName = "RESULT", Namespace = "", IsNullable = false)]

    public class Result

    {

        public string Message { get; set; }

        public ElementsWrapper FOO { get; set; }

        public override string ToString() 

        {

            var ser = new XmlSerializer(GetType());

​

            using (var stream = new StringWriter())

            {

                ser.Serialize(stream, this);

                return stream.ToString();

            }

        }

    }

    public class ElementsWrapper : IXmlSerializable

    {   

        public XElement[] Elements { get; set; }

        public XmlSchema GetSchema()

        {

            return null;

        }

        public void ReadXml(XmlReader reader)

        {

        }

        public void WriteXml(XmlWriter writer)

        {

            foreach (var element in Elements)

            {

                element.WriteTo(writer);

            }

        }

    }

}