Cannot serialize System.Web.UI.WebControls.Unit

Question

It creates a node for the property[Width] but the value is always empty. Code is below.

private static string SerializeToXml<T>(T value)
{
    StringWriter writer = new StringWriter(CultureInfo.InvariantCulture);
    XmlSerializer serializer = new XmlSerializer(typeof(T));
    serializer.Serialize(writer, value);
    return writer.ToString();
}

private static T DeSerializeToObject<T>(string xml) where T : new()
{
    try
    {
        T result;
        XmlSerializer serializer = new XmlSerializer(typeof(T));
        using (TextReader reader = new StringReader(xml))
        {
            result = (T)serializer.Deserialize(reader);
        }
        return result;
    }
    catch (Exception e)
    {
        return new T();
    }
}

public string Serialize(GridLayout layout)
{
    return SerializeToXml(layout);
}

public GridLayout DeSerialize(string xml)
{
    return DeSerializeToObject<GridLayout>(xml);
}


[Serializable]
[XmlInclude(typeof(Unit))]
public class ColumnLayout
{
    public int OrderIndex { get; set; }
    public string UniqueName { get;  set; }
    public string CurrentFilterValue { get; set; }
    public GridKnownFunction CurrentFilterFunction { get; set; }
    public string SortExpression { get; set; }
    public bool Visible { get; set; }
    public Unit Width { get; set; }
    public string HeaderText { get; set; }
    public bool IsEmpty { get; set; }
    public UnitType Type { get; set; }
    public double Value { get; set; }
}