C# Xml Serializing List<T> descendant with Xml Attribute

Morning Guys,

I have a collection that descends from List and has a public property. The Xml serializer does not pick up my proeprty. The list items serialize fine. I have tried the XmlAttribute attribute to no avail. Do you guys have a solution?

    public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }
    private void button1_Click(object sender, RoutedEventArgs e)
    {
        var people = new PersonCollection
        {
            new Person { FirstName="Sue", Age=17 },
            new Person { FirstName="Joe", Age=21 }
        };
        people.FavoritePerson = "Sue";

        var x = new XmlSerializer(people.GetType());
        var b = new StringBuilder();
        var w = XmlTextWriter.Create(b, new XmlWriterSettings { NewLineChars = "\r\n", Indent = true });
        x.Serialize(w, people);
        var s = b.ToString();
    }
}

[XmlRoot(ElementName="People")]
public class PersonCollection : List<Person>
{
    //DOES NOT WORK! ARGHHH
    [XmlAttribute]
    public string FavoritePerson { get; set; }    
}

public class Person
{
    [XmlAttribute]
    public string FirstName { get; set; }
    [XmlAttribute]
    public int Age { get; set; }
}

I'm getting the following xml

<?xml version="1.0" encoding="utf-16"?>
        <People xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
          <Person FirstName="Sue" Age="17" />
          <Person FirstName="Joe" Age="21" />
        </People>

I would like to get this

<?xml version="1.0" encoding="utf-16"?>
        <People FavoritePerson="Sue" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
          <Person FirstName="Sue" Age="17" />
          <Person FirstName="Joe" Age="21" />
        </People>