<Window x:Class="WpfApplication1.Window2"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:WpfApplication1"
        Title="Window2" Height="300" Width="300" Loaded="Window2_OnLoaded">
    <Window.Resources>
        <DataTemplate x:Key="T1">
            <TextBlock Text="{Binding}" Background="DarkBlue" Foreground="White" Padding="10,0"></TextBlock>
        </DataTemplate>
        
        <DataTemplate x:Key="T2">
            <TextBlock Text="{Binding}" Background="DarkCyan" Foreground="White" Padding="10,0"></TextBlock>
        </DataTemplate>

        <local:CTemplateSelector x:Key="TS"></local:CTemplateSelector>
    </Window.Resources>
    <Grid>
        <ListBox x:Name="Lbox" ItemTemplateSelector="{StaticResource TS}"></ListBox>
    </Grid>
</Window>

public partial class Window2 : Window
{
    public Window2()
    {
        InitializeComponent();
    }

    private void Window2_OnLoaded(object sender, RoutedEventArgs e)
    {
        var source = new List<string>
        {
            "1","2","3","4"
        };

        this.Lbox.ItemsSource = source;
    }
}

public class CTemplateSelector:DataTemplateSelector
{
    public override DataTemplate SelectTemplate( object item, DependencyObject container )
    {
        if (item == null) throw new ArgumentNullException("item");

        var element = container as FrameworkElement;

        if ( element != null )
        {
            var str = item.ToString();
            int val;

            if (int.TryParse(str, out val))
            {
                if (val%2 == 0)
                {
                    return element.FindResource("T1") as DataTemplate;
                }
                else
                {
                    return element.FindResource( "T2" ) as DataTemplate;
                }
            }
        }

        return base.SelectTemplate(item, container);
    }
}