Public MustInherit Class ISSelectionItemControl 
   Inherits ISContentControl
   Implements IControl, IFramework, ISelectionItem 

Dim instance As ISSelectionItemControl

public abstract class ISSelectionItemControl : ISContentControl, IControl, IFramework, ISelectionItem  

public class ISSelectionItemControl = class(ISContentControl, IControl, IFramework, ISelectionItem)abstract; 

public abstract class ISSelectionItemControl extends ISContentControl implements IControl, IFramework, ISelectionItem 

public __gc abstract class ISSelectionItemControl : public ISContentControl, IControl, IFramework, ISelectionItem  

public ref class ISSelectionItemControl abstract : public ISContentControl, IControl, IFramework, ISelectionItem  

<Intersoft:DockPanel HorizontalAlignment="Center" VerticalAlignment="Center">
        <Intersoft:UXListBox x:Name="ListBox1" HorizontalAlignment="Center" VerticalAlignment="Center">
                <Intersoft:UXListBoxItem Content="Item #1" IsSelected="True"/>
                <Intersoft:UXListBoxItem Content="Item #2"/>
                <Intersoft:UXListBoxItem Content="Item #3"/>
                <Intersoft:UXListBoxItem Content="Item #4"/>
        </Intersoft:UXListBox>
        <Intersoft:FieldLabel Intersoft:DockPanel.Dock="Top" Header="SelectedIndex">
                <TextBlock Text="{Binding SelectedIndex, ElementName=ListBox1}" Margin="4"/>
        </Intersoft:FieldLabel>
        <Intersoft:FieldLabel Intersoft:DockPanel.Dock="Top" Header="SelectedItem">
                <TextBlock Text="{Binding SelectedItem.Content, ElementName=ListBox1}" Margin="4"/>
        </Intersoft:FieldLabel>
        <Button Intersoft:DockPanel.Dock="Top" Content="Set Item #4.IsSelected = True" Margin="4" Click="Button_Click"/>          
</Intersoft:DockPanel>

private void Button_Click(object sender, System.Windows.RoutedEventArgs e)
{
    ((UXListBoxItem)this.ListBox1.Items[3]).IsSelected = true;
}