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

XAML 

<UserControl.Resources>
    <DataTemplate x:Key="OrderDetailsTemplate">
        <Grid>
           ...
        </Grid>
    </DataTemplate>
    <telerik:HierarchicalDataTemplate x:Key="OrderTemplate"
            ItemsSource="{Binding OrderDetailsCollection}"
            ItemTemplate="{StaticResource OrderDetailsTemplate}">
        <StackPanel Orientation="Horizontal">
           ...
        </StackPanel>
    </telerik:HierarchicalDataTemplate>
    <telerik:HierarchicalDataTemplate x:Key="CompanyTemplate"
            ItemsSource="{Binding OrdersCollection}"
            ItemTemplate="{StaticResource OrderTemplate}">
        <StackPanel Orientation="Horizontal">
           ...
        </StackPanel>
    </telerik:HierarchicalDataTemplate>
</UserControl.Resources>
<Grid x:Name="LayoutRoot" Background="White">
    <telerik:RadTreeView x:Name="treeView1" ItemsSource="{Binding CustomersCollection}"
            ItemTemplate="{StaticResource CompanyTemplate}" />
</Grid>

C#

public partial class MainPage : UserControl
{
    public MainPage()
    {
        InitializeComponent();
 
        DataContext = new NorthwindEntities();
    }
}

The approach is the same as in the RadGridView post. Again, I’ve used 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;
        }
    }
}

Demo: TreeView, MVVM and OData

In addition, you can check our online TreeView OData example.


About the Author

Kiril Stanoev

Hi, I'm Kiril and I'm the Product Manager of Telerik UI for Android, Windows Universal and Windows Phone. Feel free to ping me on +KirilStanoev or @KirilStanoev

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