<Grid x:Name="LayoutRoot" Background="White">
    <Grid.Resources>
       <local:DateFormatter x:Key="FormatConverter" />
    </Grid.Resources>

    <ComboBox Height="60" Width="200" x:Name="MusicCombo" 
        ItemsSource="{Binding}">
        <ComboBox.ItemTemplate>
            <DataTemplate>
                <StackPanel>
                    <TextBlock FontWeight="Bold" Text="{Binding Path=Name, Mode=OneWay}" />
                    <TextBlock Text="{Binding Path=Artist, Mode=OneWay}" />
                    <TextBlock Text="{Binding Path=ReleaseDate, Mode=OneWay,
                    Converter={StaticResource FormatConverter}, 
                    ConverterParameter=\{0:d\}}" />
               </StackPanel>
            </DataTemplate>
        </ComboBox.ItemTemplate>
    </ComboBox>
</Grid>

using System.Collections.ObjectModel;
using System.Windows.Data;


...


public partial class Page : UserControl
{

    public ObservableCollection<Recording> MyMusic =
        new ObservableCollection<Recording>();
    public Page()
    {
        InitializeComponent();

        // Add items to the collection.
        MyMusic.Add(new Recording("Chris Sells", "Chris Sells Live",
            new DateTime(2008, 2, 5)));
        MyMusic.Add(new Recording("Luka Abrus",
            "The Road to Redmond", new DateTime(2007, 4, 3)));
        MyMusic.Add(new Recording("Jim Hance",
            "The Best of Jim Hance", new DateTime(2007, 2, 6)));

        // Set the data context for the combo box.
        MusicCombo.DataContext = MyMusic;
    }
}

// Simple business object.
public class Recording
{
    public Recording() { }
    public Recording(string artistName, string cdName, DateTime release)
    {
        Artist = artistName;
        Name = cdName;
        ReleaseDate = release;
    }
    public string Artist { get; set; }
    public string Name { get; set; }
    public DateTime ReleaseDate { get; set; }
}

public class DateFormatter : IValueConverter
{
    // This converts the DateTime object to the string to display.
    public object Convert(object value, Type targetType, object parameter,
        System.Globalization.CultureInfo culture)
    {
        // Retrieve the format string and use it to format the value.
        string formatString = parameter as string;
        if (!string.IsNullOrEmpty(formatString))
        {
            return string.Format(culture, formatString, value);

        }
        // If the format string is null or empty, simply call ToString()
        // on the value.
        return value.ToString();
    }

    // No need to implement converting back on a one-way binding 
    public object ConvertBack(object value, Type targetType, 
        object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}