C# XML nullable attribute

Question

I'd like to have an enum attribute to be optional.
I guess the way to achieve that would be for it to be nullable.

[XmlAttribute(AttributeName = "action")]
public EAction? Action
{
    get;
    set;
}

But this won't work.

With my current knowledge on the matter the only valid nullable tpye I could use is string.
But if it's possible I'd rather not use the trick where you just hide the Enum with a string.

[XmlIgnore]
public EAction? Action
{
    get;
    set;
}

[XmlAttribute(AttributeName = "action")]
public string _Action
{
    get { return this.Action.ToString();
    set { ... }
}

Am I asking for the impossible?

Answer 1

I'm not trying to have nullable attributes now.

Instead I'm using the ShouldSerialize pattern (which I recently found out about).
So after adding a "None" value to my enum, it goes like this:

    [XmlAttribute(AttributeName = "action")]
    public EAction Action
    {
        get;
        set;
    }

    public bool ShouldSerializeAction()
    {
        return this.Action != EAction.None;
    }