The simple way is to use default behavior of the XmlSerializer by defining
the new method returning something that the XmlSerializer can simply serialize
be itself:

[XmlRoot("Task")]
public class CustomSerialization1 : IXmlSerializable
{ ...

[XmlIgnore()]
public string Test
{
...
}

[XmlArray("Test")]
[XmlArrayItem("TestInnner")]
public string[] TestAsArray
{
   get { return _s.Split(','); }
   set { _s = string.Join(",", value); }
}

another (and more complicated approach) is to use the IXmlSerializable interface.
By overriding ReadXml and WriteXml you can control the Xml serialization
by yourselves. E.g.

public class CustomSerialization1 : IXmlSerializable
{  .....
       public void WriteXml(XmlWriter writer)
       {
           .....
           writer.WriteStartElement("Test");
           foreach (string s in _s.Split(','))
           {
               writer.WriteElementString("TestInnerValue", s);
           }
           writer.WriteEndElement();
          .....
       }
.... }

Alex
http://devkids.blogspot.com