Binding to RadTreeViewItem IsSelected

I need to select an item in the tree and I am using ItemSource to generate the elements on the tree so I do not have a reference to the node.

I tried to use this example but IsSelected in my view model is not set or retreived:

http://www.telerik.com/forums/radtreeview-selecteditem-binding

My code:

                            <telerik:RadTreeListView x:Name="treeFileSystem" IsBusy="{Binding IsBusy}" RowIndicatorVisibility="Collapsed"    
                                   IsReadOnly="True" AutoGenerateColumns="False" ItemsSource="{Binding FoldersOnDemand, IsAsync=True}" IsExpandedBinding="{Binding IsExpanded, Mode=TwoWay}"
                                   AutoExpandItems="False"  Grid.Row="0" SelectionChanged="treeFileSystem_SelectionChanged">
                                <telerik:RadTreeListView.ItemContainerStyle>
                                    <Style TargetType="telerik:RadTreeViewItem">
                                        <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}" />
                                    </Style >
                                </telerik:RadTreeListView.ItemContainerStyle>

What it the correct approach to select the item in the tree?  I know the full path and I know which item it is in the view model.

Thanks