Vista - DataSourceProvider problem

I'm trying to implement a custom DataSourceProvider on Nov CTP

public class MyDataSourceProvider : DataSourceProvider
{
private MyColl coll=new MyColl();

public MyDataSourceProvider ()
{
}

protected override void BeginQuery()
{
coll.Add(new Item());
coll.Add(new Item());
coll.Add(new Item());
base.OnQueryFinished(coll);
}
}

Using :
<ObjectDataProvider x:Key="Test" ObjectType="{x:Type
local:MyDataSourceProvider}" IsAsynchronous="True" />

I can invoke the constructor but BeginQuery is never invoked so I have
problems accessing later the Data property, Am I missing something?

--
Corrado Cavalli [Microsoft .NET MVP-MCP]
UGIdotNET - http://www.ugidotnet.org
Weblog: http://blogs.ugidotnet.org/corrado