Why does deserialization fail?

[senglory]

XML:

<?xml version="1.0" encoding="utf-8" ?>
<TTTTModel>
    <TTTTClass>
        <TTTTType>Deployment</TTTTType>
        <TTTTDate>2009-09-30T00:00:00-07:00</TTTTDate>
    </TTTTClass>
    <TTTTClass>
        <TTTTType>Deployment</TTTTType>
        <TTTTDate>2009-09-20T00:00:00-07:00</TTTTDate>
    </TTTTClass>
    <TTTTClass>
        <TTTTType>Copy</TTTTType>
        <TTTTDate>2009-02-23T00:00:00-07:00</TTTTDate>
    </TTTTClass>
</TTTTModel>

The code:

[Serializable]
    public class ActionClass
    {
        [XmlElement(Form=XmlSchemaForm.Unqualified)]
        public string ActionType { get; set; }
        [XmlElement(Form = XmlSchemaForm.Unqualified)]
        public DateTime ActionDate { get; set; }
    }




    public class ActionModel : List<ActionClass>
    {
        public ActionModel()
        {
            XmlSerializer xs = new XmlSerializer(typeof(ActionModel), "");

            using (Stream ms = new FileStream("Demo.xml", FileMode.Open, FileAccess.Read))
            {
                object inp = xs.Deserialize(ms);
                this.AddRange((ActionModel)inp);
            }
        }
    }

Why I get exception on object inp = xs.Deserialize(ms)?

<ActionModel xmlns=''> was not expected.

How to fix it?