<UserControl
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:Intersoft="http://intersoft.clientui.com/schemas"
        xmlns:local="clr-namespace:ClientUI.Sample"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"      
        mc:Ignorable="d"
        x:Class="ClientUI.Sample.MainPage" Width="800" Height="600">
    <UserControl.Resources>
        <Style x:Key="ItemStyle1" TargetType="Intersoft:UXListBoxItem">
            <Setter Property="Background" Value="Gold"/>
        </Style>
        <Style x:Key="ItemStyle2" TargetType="Intersoft:UXListBoxItem">
            <Setter Property="Background" Value="Silver"/>
        </Style>
        <local:AlternateStyleSelector x:Key="AlternateStyleSelector" ItemStyle="{StaticResource ItemStyle1}" AlternateItemStyle="{StaticResource ItemStyle2}"/>
    </UserControl.Resources>
    <Grid>
        <Intersoft:UXListBox x:Name="ListBox1" HorizontalAlignment="Center" VerticalAlignment="Center" ItemContainerStyleSelector="{StaticResource AlternateStyleSelector}">
            <Intersoft:UXListBoxItem Content="Item #1"/>
            <Intersoft:UXListBoxItem Content="Item #2"/>
            <Intersoft:UXListBoxItem Content="Item #3"/>
            <Intersoft:UXListBoxItem Content="Item #4"/>
        </Intersoft:UXListBox>
    </Grid>
</UserControl>

using System.Windows;
using Intersoft.Client.Framework;
using Intersoft.Client.UI.Aqua.UXCollection;

namespace ClientUI.Sample
{
    public class AlternateStyleSelector: StyleSelector
    {
        public Style ItemStyle { get; set; }

        public Style AlternateItemStyle { get; set; }

        public override Style SelectStyle(object item, DependencyObject container)
        {
            UXListBoxItem control = container as UXListBoxItem;
            if (control != null)
            {
                UXListBox owner = control.Owner as UXListBox;
                if (owner.Items.IndexOf(control) % 2 == 0)
                    return this.ItemStyle;
            }

            return this.AlternateItemStyle;
        }
    }
}