Design-time data supported by entities?

I'm trying to create design-time XAML for Silverlight(VS2012, not Blend). I have no problem creating single-object representation but nested childs don't work. Here is XAML I have: 

<MaintainTruckViewModel 
    xmlns="clr-namespace:IDATT.Module.Assets.Views"
    xmlns:data="clr-namespace:IDATT.Model;assembly=IDATT.Model.SL">
    <MaintainTruckViewModel.CurrentItem>
        <data:ASTTruck
            TruckId="1000"
            ExternalTruckId="T1000"
            IsActive="True"
            VinNumber="1ZAXBV"
            Make="Volvo"
            Model="ABC"
            MakeYear="2010"
            PlateNumber="ABC 123"
            PlateIssueAdministrativeArea="MO"
            Height="110"
            AxlesCount="3">
            <data:ASTTruck.ASTInsurances>
                <data:ASTInsurance
                    InsuranceKey="1"
                    CompanyName="MainCo"
                    AgentCompanyName="Joes insurance"
                    CoverageAmount = "1000000"
                    DeductibleAmount = "1000"
                    InsuranceType = "General liability"
                    IsActive = "True"
                    PolicyNumber = "123ABC"
                    ExpireOn = "01-01-2012"
                    Note = "This insurance covers all stuff"/>
            </data:ASTTruck.ASTInsurances>
        </data:ASTTruck>
    </MaintainTruckViewModel.CurrentItem>
</MaintainTruckViewModel>    

This is VM object, IdeaBlade entity represented as CurrentItem property
Single ASTTruck have multiple ASTInsurance, those are entities.

I guess I build childs improperly, designer doesn't complain about XAML though..

Here is where I bind to list:

<ItemsControl ItemsSource="{Binding CurrentItem.ASTInsurances}">

It works at runtime but doesn't work at design time.
Is there any best practices to fake entities for design-time support?

Edited by katit - 03-Jan-2013 at 1:08pm