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Binding to WCF Service

Updated on Sep 24, 2025

The purpose of this tutorial is to show you how to populate a RadTreeView with data from a WCF Service.

This tutorial will use the Northwind database, which can be downloaded from here.

Here will be examined "best practice" for using RadTreeView with load on demand and WCF Service.

Add a new RadTreeView declaration in your XAML and add an event handler for LoadOnDemand event. Also set the following properties to True:
- IsLoadOnDemandEnabled
- IsExpandOnSingleClickEnabled
XAML
```
	<telerik:RadTreeView x:Name="radTreeView" Margin="8"
	   IsLoadOnDemandEnabled="True" IsExpandOnSingleClickEnabled="True"
	   LoadOnDemand="radTreeView_LoadOnDemand"/>
```
The treeview will be bound to a data source object, that has a property Categories. When the LoadOnDemand event of RadTreeView is fired, the selected category asynchronously loads its related products.
Create a new class named NorthwindDataSource.
C#
```
	public class NorthwindDataSource
	{
	}
```
Add a reference to your WCF Service
In the NorthwindDataSource class add a reference to an ObservableCollection of Categories.

In the NorthwindDataSource class add a reference to your WCF Service client:

	public class NorthwindDataSource
	{
		private SampleWcfServiceClient serviceClient;
		public NorthwindDataSource()
		{
			serviceClient = new SampleWcfServiceClient();
			this.Categories = new ObservableCollection<Categories>();
		}
		public ObservableCollection<Categories> Categories
		{
			get;
			set;
		}
	}

Add the following code in the constructor of the NorthwindDataSource. It will make the initial load of all Categories from the database:

	this.serviceClient.LoadCategoriesCompleted += new EventHandler<LoadCategoriesCompletedEventArgs>( serviceClient_LoadCategoriesCompleted );
	this.serviceClient.LoadCategoriesAsync();

	foreach ( Categories c in serviceClient.LoadCategories() )
	{
		this.Categories.Add( c );
	}

Update your treeview declaration - set the ItemsSource and ItemTemplate properties.

XAML

	<telerik:RadTreeView x:Name="radTreeView" Margin="8"
		IsLoadOnDemandEnabled="True" IsExpandOnSingleClickEnabled="True"
		LoadOnDemand="radTreeView_LoadOnDemand"
		ItemTemplate="{StaticResource CategoryTemplate}"
		ItemsSource="{Binding Source={StaticResource DataSource}, Path=Categories}"/>

Run your demo, the result can be seen on the next picture:

WPF RadTreeView Binding to WCF Service Data

If you try to expand any of the loaded categories, the default load on demand animation will be started:

WPF RadTreeView Load On Demand Animation

The next step is to handle the load on demand event.

Add the following method to the NorthwindDataSource class, which aims to load the products for the expanded category:

	public void BeginLoadingProducts( Categories category )
	{
		serviceClient.LoadProductsByCategoryIdCompleted += new EventHandler<LoadProductsByCategoryIdCompletedEventArgs>( serviceClient_LoadProductsByCategoryIdCompleted );
		serviceClient.LoadProductsByCategoryIdAsync( category.CategoryID, category );
	}
	private void serviceClient_LoadProductsByCategoryIdCompleted( object sender, LoadProductsByCategoryIdCompletedEventArgs e )
	{
		if ( e.Error == null && e.Result != null )
		{
			Categories currentCategory = e.UserState as Categories;
			foreach ( Products p in e.Result )
			{
				currentCategory.Products.Add( p );
			}
		}
	}

	public void LoadProducts( Categories category )
	{
		category.Products = new ObservableCollection<Products>();
		foreach ( Products p in serviceClient.LoadProductsByCategoryId( category.CategoryID ) )
		{
			category.Products.Add( p );
		}
	}

The body of the exposed LoadProductsByCategoryId() method is shown on the code snippet below.

	[OperationContract]
	public List<Products> LoadProductsByCategoryId( int categoryId )
	{
		NorthwindEntities ent = new NorthwindEntities();
		var q = from p in ent.Products
				where p.Categories.CategoryID == categoryId
				orderby p.ProductName
				select p;
		return q.ToList();
	}

Add the following code to the load on demand event handler, which you declared on step 1.

	private void radTreeView_LoadOnDemand( object sender, Telerik.Windows.RadRoutedEventArgs e )
	{
		RadTreeViewItem item = e.OriginalSource as RadTreeViewItem;
		Categories category = item.Item as Categories;
		if ( category != null )
		{
			( this.Resources[ "DataSource" ] as NorthwindDataSource ).BeginLoadingProducts( category );
		}
		else
		{
			item.IsLoadOnDemandEnabled = false;
		}
	}

When there are no items to add, and you want to prevent the LoadOnDemand event to fire again, set the IsLoadOnDemandEnabled property to False to the RadTreeViewItem that has fired the LoadOnDemand event.

And here is the result:

WPF RadTreeView Bound to WCF Service Data

Binding to WCF Service

See Also