System.Uri implements ISerializable, but gives error? [duplicate]

Question

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.

Answer 1

In order to be serialized to XML, Uri class should have a parameterless constructor, which it doesn't: Uri is designed to be immutable. Honestly, I can't see why it cannot be serialized without having a parameterless constructor.

To circumvent this, either change URI property type to string, or add one more property called _URI, mark URI with XmlIgnoreAttribute and rewrite it's get method as get { return new Uri(_URI); }.

Answer 2

You're confusing binary serialization with XML serialization.

XML serialization is a very simple process that saves field values and restores into a new object.

Binary serialization is much more powerful, and allows the object to control serialization behavior. The ISerializable interface, which Uri does implement, is only used for binary serialization.