LinqToXml does not handle nillable elements as expected

Question

According to W3C standards, if you have a nillable element with a nil value, you are supposed to format it like this:

Answer 1

Hopefully, this is not the ideal answer, but I wrote a couple extension methods to at least make it a little easier to deal with nillable elements in LinqToXml.

Extension Methods:

public static class XElementExtensions
{
    private static XName _nillableAttributeName = "{http://www.w3.org/2001/XMLSchema-instance}nil";

    public static void SetNillableElementValue(this XElement parentElement, XName elementName, object value)
    {
        parentElement.SetElementValue(elementName, value);
        parentElement.Element(elementName).MakeNillable();
    }

    public static XElement MakeNillable(this XElement element)
    {
        var hasNillableAttribute = element.Attribute(_nillableAttributeName) != null;
        if (string.IsNullOrEmpty(element.Value))
        {
            if (!hasNillableAttribute)
                element.Add(new XAttribute(_nillableAttributeName, true));
        }
        else
        {
            if (hasNillableAttribute)
                element.Attribute(_nillableAttributeName).Remove();
        }
        return element;
    }
}

Example Usage

// "nil" attribute will be added
element.Add(
    new XElement(NS + "myNillableElement", null)
    .MakeNillable();

// no attribute will be added
element.Add(
    new XElement(NS + "myNillableElement", "non-null string")
    .MakeNillable();

// "nil" attribute will be added (if not already present)
element.SetNillableElementValue(NS + "myNillableElement", null);

// no attribute will be added (and will be removed if necessary)
element.SetNillableElementValue(NS + "myNillableElement", "non-null string");