为什么XmlSerializer不能序列化这个列表对象?

下面是我的代码:

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        PaneData data = new PaneData();
        data.Add("S1");
        data.Add("S2");
        data.SerializableLogFilters.Add("S3");
        XmlSerializer serializer = new XmlSerializer(typeof(PaneData));
        FileStream stream = new FileStream("Test.xml", FileMode.Create);
        StreamWriter streamWriter = new StreamWriter(stream);
        serializer.Serialize(streamWriter, data);
        streamWriter.WriteLine(String.Empty);
        streamWriter.Flush();
        stream.Close();
    }
    public class PaneData : IEnumerable<string>, INotifyCollectionChanged
    {
        public List<string> RowList { get; set; }
        public List<string> SerializableLogFilters { get; set; }
        public event NotifyCollectionChangedEventHandler CollectionChanged;
        public PaneData()
        {
            RowList = new List<string>();
            SerializableLogFilters = new List<string>();
        }
        protected virtual void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
        {
            if (CollectionChanged != null)
            {
                CollectionChanged(this, e);
            }
        }
        public void Add(string item)
        {
            RowList.Add(item);
            OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, item));
        }
        public IEnumerator<string> GetEnumerator()
        {
            return RowList.GetEnumerator();
        }
        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        }
    }

序列化出来的结果如下:

<?xml version="1.0" encoding="utf-8"?>
<ArrayOfString xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <string>S1</string>
  <string>S2</string>
</ArrayOfString>

为什么我在序列化文件中看不到S3和第二个字符串数组?