PerfectPhase said:Coming soon in XAML-2009 non-default constructors....
<coll:List x:Key='list' x:TypeArguments='x:String' x:FactoryMethod='local:Factory.CreateStringList'>
<x:Arguments>
<x:String>Mickey,Donald</x:String>
</x:Arguments>
</coll:List>
via: http://blogs.msdn.com/llobo/archive/2009/11/20/xaml-2009-features-factorymethod-arguments.aspx
You might want to have a look at the noode stream support in System.Xaml (see PDC2008 - TL36) You can proberbly do what ever you like if you use XamlObjectReader and XamlXmlWriter rather than XamlServices.
This is great news PerfectPhase! It would be really great if it also meant that setters could be by-passed entirely.