using System;

using System.IO;

using System.Text;

using System.Xml.Serialization;

​

public class Program

{

    [XmlType(typeName: "int")]

    public enum MyEnum : int

    {       

        One,

    }

​

    public class ValueContainer

    {

        public object Value;

    }

​

    public static void Main()

    {

        var ov = new XmlAttributeOverrides(); 

        ov.Add(typeof(MyEnum), nameof(MyEnum.One), new XmlAttributes { XmlEnum = new XmlEnumAttribute("0") }); 

        var newSerializer = new XmlSerializer(typeof(ValueContainer), ov, new[] { typeof(MyEnum) }, null, null);

        var instance = new ValueContainer();

        instance.Value = MyEnum.One;

        var memoryStream = new MemoryStream();

        newSerializer.Serialize(memoryStream, instance);

        var str = Encoding.Default.GetString(memoryStream.ToArray());

        str.Dump();

    }

}