c# - When a class is inherited from List, XmlSerializer doesn't serialize other attributes

I'm having a situation here, I need my class to be inherited from List, but when I do this XmlSerializer does not serialize any property or field declared in my class, the following sample demonstrates:

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();

        DoSerialize();
    }
    private void DoSerialize()
    {
        MyClass obj = new MyClass();
        obj.Add(1);
        obj.Add(2);
        obj.Add(3);
        XmlSerializer s = new XmlSerializer(typeof(MyClass));
        StringWriter sw = new StringWriter();

        s.Serialize(sw, obj);
    }
}
[Serializable]
[XmlRoot]
public class MyClass : List
{
    public MyClass()
    {
    }

    int myAttribute = 2011;
    [XmlAttribute]
    public int MyAttribute
    {
        get
        {
            return myAttribute;
        }
        set
        {

            myAttribute = value;
        }
    }
}

the resulting XML:

  1
  2
  3

Answer

This is by design. I don't know why this decision was made, but it is stated in the documentation:

• Classes that implement ICollection or IEnumerable. Only collections are
  serialized, not public properties.

(Look under "Items that can be serialized" section). Someone has filed a bug against this, but it won't be changed - here, Microsoft also confirms that not including the properties for classes implementing ICollection is in fact the behaviour of XmlSerializer.

A workaround would be to either:

• Implement IXmlSerializable and control serialization yourself.

or

• Change MyClass so it has a public property of type List (and don't subclass it).

or

• Use DataContractSerializer, which handles this scenario.