Maybe not exactly what you want, but you can get close like this:

public class Foo
{
ArrayList _classNames = new ArrayList();
[XmlArray("ClassNames"), XmlArrayItem("ClassName")]
public string[] ClassNames
{
 get { return (string[])_classNames.ToArray(typeof(string)); }
 set {_classNames = new ArrayList(value);}
}
}

Construct and serialize a Foo like this:

string[] names = new string[]{"f", "g", "h"};
Foo f = new Foo();
f.ClassNames = names;
Console.WriteLine(SerializeThingToXmlString(f));

Where the helper method is:

static string SerializeThingToXmlString(object thing)
{
StringWriter stringWriter = new StringWriter();
XmlSerializer serializer = new XmlSerializer(thing.GetType());
serializer.Serialize(stringWriter, thing);
return stringWriter.ToString();
}

Hi, Bob.
 One solution I can think right out-of-the box is:

 public class Classnames {
     [XmlElement("Classname")]
     public Classname[] Members;
     ......
 }

 By applying XmlElementAttribute to an array, You can eliminate the
ArrayOfClassname/Members element from the serialized result. And by wrapping
the array in a class named Classnames, you can make sure the result Xml has
a Classnames root element. The net effect is that you get an Xml document
that has a Classnames root and a list of Classname.

 On the other hand, .NET does allow XmlXXXAttributes to be applied on
function return value. But there isn't any easy way to leverage it. E.g:
WebService engine utilizes this through XmlMapping, which is marked "not
intended to be used directly from your code" in MSDN. I think that you can
still use XmlMapping classes, though.

 Hope this helps.
 Ming Chen [.NET MVP]