Change the Appearance of a List Item When It's Selected

   
  

<Window x:Class="WpfApplication1.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:WpfApplication1="clr-namespace:WpfApplication1;assembly="
    Title="WPF" Height="248" Width="128">
    <Window.Resources>

        <WpfApplication1:Countries x:Key="countries"/>

        <Style TargetType="{x:Type ListBoxItem}">
            <Setter Property="Content" Value="{Binding Path=Name}"/>
            <Setter Property="Margin" Value="20"/>
            <Style.Triggers>
                <Trigger Property="IsSelected" Value="True">
                    <Setter Property="FontWeight" Value="Bold" />
                    <Setter Property="FontSize" Value="14" />
                </Trigger>
            </Style.Triggers>
        </Style>
    </Window.Resources>

    <Grid>
        <ListBox ItemsSource="{Binding Source={StaticResource countries}}"/>
    </Grid>

</Window>
//File:Window.xaml.cs
using System.Collections.ObjectModel;

namespace WpfApplication1
{
    public class Country
    {
        private string name;
        private Continent continent;

        public Country(string name, Continent continent)
        {
            this.name = name;
            this.continent = continent;
        }

        public string Name
        {
            get
            {
                return name;
            }
            set
            {
                name = value;
            }
        }

        public Continent Continent
        {
            get
            {
                return continent;
            }
            set
            {
                continent = value;
            }
        }

    }

    public enum Continent
    {
        Europe,
        NorthAmerica,
    }

    public class Countries : Collection<Country>
    {
        public Countries()
        {
            this.Add(new Country("Great Britan", Continent.Europe));
            this.Add(new Country("USA", Continent.NorthAmerica));
            this.Add(new Country("Canada", Continent.NorthAmerica));
        }    
    }
}