System.Uri implements ISerializable, but gives error?

Possible Duplicate:
How to (xml) serialize a uri

To my knowledge Uri implements ISerializable, but throws error when used like this:

XmlSerializer xs = new XmlSerializer(typeof(Server));
xs.Serialize(Console.Out, new Server { Name = "test", URI = new Uri("http://localhost/") });

public class Server
{
    public string Name { get; set; }
    public Uri URI { get; set; }
}

Works just fine if Uri type is changed to string.

Anyone knows what is the culprit?

Solution proposed by Anton Gogolev:

public class Server
{
    public string Name { get; set; }

    [XmlIgnore()]
    public Uri Uri; 
    
    [XmlElement("URI")]
    public string _URI // Unfortunately this has to be public to be xml serialized.
    { 
        get { return Uri.ToString(); }
        set { Uri = new Uri(value); }
    }
}

(Thanks for SLaks also pointing out the backwardness of my method...)

This produces XML output:

<Server>
    <URI>http://localhost/</URI>
    <Name>test</Name>
</Server>

I rewrote it here so the code is visible.