If you want to select an item you need to set the RadTreeViewItem's IsSelected property to True.

CopyXAML

<telerik:RadTreeViewItem x:Name="radTreeViewItem" IsSelected="True"/>

CopyC#

radTreeViewItem.IsSelected = true;

CopyVB.NET

radTreeViewItem.IsSelected = True

Note
Note, that the code snippets above cover scenario when your RadTreeView is populated declaratively (with static data). If you want to bind the IsSelected property to a property of a custom business object, check out the Binding the IsSelected Property section at the end of this topic.

Another way to select a treeview item programmatically is to add it to the SelectedItems collection of the RadTreeView class. There are two possible cases here, depending on how the RadTreeView is populated.

• If your RadTreeView is populated declaratively in XAML (with static data), then the SelectedItems collection will contain instances of the RadTreeViewItem class.

CopyC#

radTreeView.SelectedItems.Add( radTreeViewItem );

CopyVB.NET

radTreeView.SelectedItems.Add(radTreeViewItem)

• In case your RadTreeView is data bound to a business object, then the situation is different. The SelectedItems collection will contain instances of your business object.

CopyC#

radTreeView.SelectedItems.Add( myViewModel );

CopyVB.NET

radTreeView.SelectedItems.Add(myViewModel)

The RadTreeView API allows you to change the selection mode of the treeview. You need to set the SelectionMode property to do that. The SelectionMode property is a SelectionMode enumeration which exposes the following members:

• Single - use it for a single selection. At this mode the user will be available to select only one item at once.

• Multiple and Extended - use that values when you want the user to be able to select multiple items at one time by holding down the Ctrl or Shift keys and clicking multiple items with the mouse or by using the keyboard. A second click on a selected item will unselect that item.

Note

There are two SelectionMode enumerations: System.Windows.Controls.SelectionMode Telerik.Windows.Controls.SelectionMode If you intend to change the SelectionMode in the code-behind you need to use the second one: CopyC# private void ChangeSelectionMode() { radTreeView.SelectionMode = Telerik.Windows.Controls.SelectionMode.Multiple; } CopyVB.NET Private Sub ChangeSelectionMode() radTreeView.SelectionMode = Telerik.Windows.Controls.SelectionMode.Multiple End Sub

The next example demonstrates you how to set the SelectionMode property.

CopyXAML

<telerik:RadTreeView x:Name="radTreeView" SelectionMode="Multiple">

As you can see from the snapshot below, now you are able to select more than on item (node).

Tip
The default selection of the RadTreeView is Single.

RadTreeView class exposes several properties which allow you to access the currently selected item(s).

• SelectedItem - returns the currently selected item.
• SelectedItems - this property returns a collection representing the currently selected items. It is appropriate to use SelectedItems property when you have multiple selected items. SelectedItems is a ObservableCollection of objects.
• SelectedContainer - gets the current selected item container. This property is always of type RadTreeViewItem.

Again, you have two possible cases:

• Your RadTreeView is populated declaratively in XAML (with static data). In this case, the SelectedItem and SelectedContainer properties will return you objects of type RadTreeViewItem. Respectively the SelectedItems collection contains RadTreeViewItems.
• Your RadTreeView is data bound to a business object. In this case, the SelectedItem property will be an instance of your business object. The SelectedItems collection will contain instances of your business object. The SelectedContainer property again will return RadTreeViewItem.

Note
When you have multiple selected items, the SelectedItem property will return the first selected item in the treeview.

Note
When you reset the RadTreeView'sItems collection (when you invoke the RadTreeView.Items.Clear() method), that will result also in clearing the SelectedItems collection.

Note
Telerik RadTreeView class inherits from ItemsControl. The Items collection of the ItemsControl is a collection of data objects, not from RadTreeViewItems. There is a very important concept about the items and item containers. For more information read here.

Note
Each ItemsControl provides two additional properties for working with selection - SelectedValue and SelectedValuePath. If want to learn how to use these two properties, please check out the Using SelectedItem, SelectedValue and SelectedValuePath section at the end of this topic.

The Telerik RadTreeView and RadTreeViewItem classesoffer you five events for managing the edit process.

CopyXAML

<telerik:RadTreeView x:Name="radTreeView"
        PreviewSelected="radTreeView_PreviewSelected"
        Selected="radTreeView_Selected"
        PreviewUnselected="radTreeView_PreviewUnselected"
        Unselected="radTreeView_Unselected"
        SelectionChanged="radTreeView_SelectionChanged"/>

The PreviewSelected event occurs when the treeview item is about to be selected. The Selected event is fired when the treeview item is already selected. The type of the passed event arguments for both of the events is RadRoutedEventArgs. In the event handlers you can place some code.

For example, the next code snippet will change the FontSize of the selected item.

CopyC#

private void radTreeView_Selected( object sender, RadRoutedEventArgs e )
{
    ( e.Source as RadTreeViewItem ).FontSize = 14;
}

CopyVB.NET

Private Sub radTreeView_Selected(ByVal sender As Object, ByVal e As RadRoutedEventArgs)
    TryCast(e.Source, RadTreeViewItem).FontSize = 14
End Sub

The PreviewUnselected event is fired just before the currently selected item is unselected. The Unselected event occurs when the treeview item is already unselected. The type of the passed event arguments for both of the events is RadRoutedEventArgs.

In order to hangle a change in the selection you need to use the SelectionChanged event. This event is available only for the RadTreeView class. It is fired each time an item(s) is/are added or removed from the selection. The type of the passed event arguments for the event is SelectionChangedEventArgs. Here is a sample code for handling the SelectionChanged event.

CopyC#

private void radTreeView_SelectionChanged( object sender, Telerik.Windows.Controls.SelectionChangedEventArgs e )
{
    // Get a reference to the treeview
    Telerik.Windows.Controls.RadTreeView treeView = sender as Telerik.Windows.Controls.RadTreeView;

    // Get the currently selected items
    ObservableCollection<Object> selectedItems = treeView.SelectedItems;
    // Get the newly added items to the collection
    IList addedItems = e.AddedItems;
    // Get the removed items from the collection
    IList removedItems = e.RemovedItems;
}

CopyVB.NET

Private Sub radTreeView_SelectionChanged(ByVal sender As Object, ByVal e As Telerik.Windows.Controls.SelectionChangedEventArgs)
    ' Get a reference to the treeview
    Dim treeView As Telerik.Windows.Controls.RadTreeView = TryCast(sender, Telerik.Windows.Controls.RadTreeView)

    ' Get the currently selected items
    Dim selectedItems As ObservableCollection(Of [Object]) = treeView.SelectedItems

    ' Get the newly added items to the collection
    Dim addedItems As IList = e.AddedItems

    ' Get the removed items from the collection
    Dim removedItems As IList = e.RemovedItems
End Sub

Note
Four out of the five events (PreviewSelected, Selected, PreviewUnselected and Unselected) are exposed by both RadTreeView and RadTreeViewItem classes. While the SelectionChanged event is available only in the RadTreeView class.

The SelectedValue property is used when you have linked your RadTreeView to a data source, and you want to return a value other than the one which is displayed. The SelectedValuePath property provides a way to specify a SelectedValue for the SelectedItem in a RadTreeView. The SelectedItem represents an object in the Items collection and the RadTreeView displays the value of a single property of the selected item. The SelectedValuePath property specifies the path to the property that is used to determine the value of the SelectedValue property. The next example illustrates this concept.

Imagine that you have a business object named MyViewModel, with three members (properties): Title, Price and Children. And a RadTreeView which is data bound to a list of MyViewModel objects. The Title property is the property which is displayed. The Price is set to the SelectedValuePath property.

CopyC#

private class MyViewModel
{
    public string Title
    {
        get;
        set;
    }
    public string Price
    {
        get;
        set;
    }
    public IList<MyViewModel> Children
    {
        get;
        set;
    }
}

CopyVB.NET

Private Class MyViewModel
Private _Title As String
    Public Property Title() As String
        Get
            Return _Title
        End Get
        Set(ByVal value As String)
            _Title = value
        End Set
    End Property

Private _Price As String
    Public Property Price() As String
        Get
            Return _Price
        End Get
        Set(ByVal value As String)
            _Price = value
        End Set
    End Property

Private _Children As IList(Of MyViewModel)
    Public Property Children() As IList(Of MyViewModel)
        Get
            Return _Children
        End Get
        Set(ByVal value As IList(Of MyViewModel))
            _Children = value
        End Set
    End Property
End Class

CopyXAML

<telerik:RadTreeView x:Name="radTreeView" SelectedValuePath="Price">
    <telerik:RadTreeView.ItemTemplate>
        <HierarchicalDataTemplate ItemsSource="{Binding RelatedItems}">
            <TextBlock Text="{Binding Title}" />
        </HierarchicalDataTemplate>
    </telerik:RadTreeView.ItemTemplate>
</telerik:RadTreeView>

When you select a MyViewModelTitle from the RadTreeView, the SelectedItem property returns the MyViewModel data item that corresponds to the selected Title. However, because the SelectedValuePath of this RadTreeView is set to the MyViewModel's Price property, the SelectedValue will return the Price property of the MyViewModel business object (e.g. 101.56$).

A very common issue is to have the RadTreeViewItem's IsSelected property bound to a property of a custom business object. The easiest way to achieve this is to use Style Binding. For example, imagine your business object has a boolean property named IsSelected. And you want to bind the IsSelected property of this business object to the IsSelected property of the RadTreeViewItem. Then check out the code snippet below, it demonstrates how to achieve this.

CopyXAML

<Style x:Key="ItemContainerStyle" TargetType="{x:Type telerik:RadTreeViewItem}">
    <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}"/>
</Style>
<HierarchicalDataTemplate  
    x:Key="MyViewModelTemplate">
    <TextBlock Text="{Binding Name}" Foreground="Red" FontSize="16" FontFamily="Verdana" />
</HierarchicalDataTemplate>
....
<telerik:RadTreeView  
    ItemsSource="{Binding Source={StaticResource TreeViewDataSource}}" 
    ItemTemplate="{StaticResource MyViewModelTemplate}"
    ItemContainerStyle="{StaticResource ItemContainerStyle}"/>

For a complete demo, please refer to the How to Bind RadTreeView to Hierarchical Data and Use Style Binding topic.

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