C# - Give A Custom Control Ability To Parse XML Markup To A Collection?

I'm writing a custom ASP.NET webcontrol and would like it to have a collection of custom items which can also be specified in the XML markup. Something like this:

class MyControl: WebControl
{
public IList<MyItemType> MyItems { get; private set; }
}

And in the markup:

<asd:MyControl runat="server" id="mc1">
<MyItems>
<MyDerivedCustomItem asd="dsa"/>
<MyOtherDerivedCustomItem asd="dsa"/>
</MyItems>
</asd:MyControl>

How do I do this? I though this was all about implementing some interface on the collection or adding some special attributes to the property, but nothing I do seems to work.