using System;

using System.Xml.Serialization;

using System.Xml;

using System.IO;

​

public enum TipoDoAmbiente

{

​

    [XmlEnumAttribute("1")]

    Item1,

​

    [XmlEnumAttribute("2")]

    Item2,

}

​

public class TesteClasse 

{

    public TipoDoAmbiente TipoDoAmbiente { get; set; }

}

public class Program

{

    public static void Main()

    {

        var xmlSerializer = new XmlSerializer(typeof(TesteClasse));

        var classe = new TesteClasse { TipoDoAmbiente = TipoDoAmbiente.Item2 };

        var stringWriter = new StringWriter();

        using (var xmlWriter = XmlWriter.Create(stringWriter))

        {

            xmlSerializer.Serialize(xmlWriter, classe);

            var xml = stringWriter.ToString(); // Seu XML

            Console.WriteLine(xml);

        }

    }

}