Unable to create a Collection Type Dependency Property

I'm trying to create a custom list which features a List of objects. Though when this is set both in the Xaml and th开发者_StackOverflowe code behind I get a "Incorrect markup error". Below is how I'm settings up the PropertyKey and Property.

private static readonly DependencyPropertyKey ItemSourcePropertyKey = DependencyProperty.RegisterReadOnly(
        "ItemSource",
        typeof(List<object>),
        typeof(MultiSelectComboBox),
        new FrameworkPropertyMetadata(null));

public static readonly DependencyProperty ItemSourceProperty = ItemSourcePropertyKey.DependencyProperty;

The Field is:

 public List<object> ItemSource
    {
        get { return (List<object>)this.GetValue(ItemSourceProperty); }
        set { this.SetValue(ItemSourceProperty, value); }
    }

The error I get is:

{"Cannot create instance of 'Window1' defined in assembly 'GroupExpansion, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'. Exception has been thrown by the target of an invocation.  Error in markup file 'Window1.xaml' Line 1 Position 9."}

Has anyone bound a DependencyProperty to a List before? I've come across a few tutorials but when I try to emulate the tutorials it falls on it's face. The List and Property are in a file which extends a UserControl. If you need any more details just ask. I've been banging my head off the keyboard now for a couple of days. Seem to be going round in circles.

Cheers

Found the solution, It would seem that the Dependency Property needs to be attached to a ObservableCollection. And then for binding it then need to be non read only so the DependencyPropertyKey can be dropped and replaced with only the DependencyProperty. Would be incredibly useful if someone set up an actual page for this.