Hierarchy Load On Demand With RadGridView for Silverlight, MVVM and OData

Similar to this post, I’ve made small example on how to load on demand RadGridView for Silverlight three level hierarchy using MVVM and OData service:
 

XAML

<telerik:RadGridView ItemsSource="{Binding CustomersCollection}" AutoGenerateColumns="False">
    <telerik:RadGridView.Columns>
        …
    </telerik:RadGridView.Columns>
    <telerik:RadGridView.ChildTableDefinitions>
        <telerik:GridViewTableDefinition />
    </telerik:RadGridView.ChildTableDefinitions>
    <telerik:RadGridView.HierarchyChildTemplate>
        <DataTemplate>
            <telerik:RadGridView ItemsSource="{Binding OrdersCollection}" AutoGenerateColumns="False">
                <telerik:RadGridView.Columns>
                    …
                </telerik:RadGridView.Columns>
                <telerik:RadGridView.ChildTableDefinitions>
                    <telerik:GridViewTableDefinition />
                </telerik:RadGridView.ChildTableDefinitions>
                <telerik:RadGridView.HierarchyChildTemplate>
                    <DataTemplate>
                        <telerik:RadGridView ItemsSource="{Binding OrderDetailsCollection}" AutoGenerateColumns="False">
                            <telerik:RadGridView.Columns>
                                …

                            </telerik:RadGridView.Columns>
                        </telerik:RadGridView>
                    </DataTemplate>
                </telerik:RadGridView.HierarchyChildTemplate>
            </telerik:RadGridView>
        </DataTemplate>
    </telerik:RadGridView.HierarchyChildTemplate>
</telerik:RadGridView>

C#

public partial class MainPage : UserControl
{
    public MainPage()
    {
        InitializeComponent();

        DataContext = new NorthwindEntities();
    }
}    

I’ve used again partial classes to extend generated code for the service reference:

C#

public partial class NorthwindEntities
{
    public NorthwindEntities()
        : base(new Uri("http://services.odata.org/Northwind/Northwind.svc"))
    {
        //
    }

    DataServiceCollection<Customer> _CustomersCollection;
    public DataServiceCollection<Customer> CustomersCollection
    {
        get
        {
            if (_CustomersCollection == null)
            {
                _CustomersCollection = new DataServiceCollection<Customer>(this);
                _CustomersCollection.CollectionChanged += (s, e) =>
                {
                    if (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Add)
                    {
                        foreach (var c in e.NewItems.OfType<Customer>())
                        {
                            c.Context = this;
                        }
                    }
                    else if (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Remove)
                    {
                        foreach (var c in e.OldItems.OfType<Customer>())
                        {
                            c.Context = null;
                        }
                    }
                };
                _CustomersCollection.LoadAsync(this.Customers);
            }
            return _CustomersCollection;
        }
    }
}

and as you can see I’ve passed the context itself to the entities in order to create queries for child data:
C#

public partial class Customer
{
    public Customer()
    {
        _Orders = null;
    }

    internal NorthwindEntities Context { get; set; }

    public DataServiceCollection<Order> OrdersCollection
    {
        get
        {
            if (_Orders == null && Context != null)
            {
                _Orders = new DataServiceCollection<Order>(Context);
                _Orders.CollectionChanged += (s, e) =>
                {
                    if (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Add)
                    {
                        foreach (var c in e.NewItems.OfType<Order>())
                        {
                            c.Context = this.Context;
                        }
                    }
                    else if (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Remove)
                    {
                        foreach (var c in e.OldItems.OfType<Order>())
                        {
                            c.Context = null;
                        }
                    }
                };
                _Orders.LoadAsync(from o in Context.Orders
                                    where o.CustomerID == CustomerID
                                    select o);
            }
            return _Orders;
        }
    }
}