Serializable and XmlEnum

The easiest way is to use [XmlEnum] attribute like so:

[Serializable]
public enum EnumToSerialize
{
    [XmlEnum("1")]
    One = 1,
    [XmlEnum("2")]
    Two = 2
}

This will serialize into XML (say that the parent class is CustomClass) like so:

<CustomClass>
  <EnumValue>2</EnumValue>
</CustomClass>