[xaml]
<Window.Resources>
        <CollectionViewSource x:Key="EmployeesSource" Source="{Binding Employees}" CollectionViewType="local:EmployeeCollectionView">

            <CollectionViewSource.GroupDescriptions>
                <PropertyGroupDescription PropertyName="HireDate"/>
            </CollectionViewSource.GroupDescriptions>

        </CollectionViewSource>

        <DataTemplate x:Key="EmployeeTemplate">
            <StackPanel Orientation="Horizontal">
                <TextBlock Text="{Binding FirstName}" />
                <TextBlock Text="{Binding LastName}" />
            </StackPanel>
        </DataTemplate>
</Window.Resources>

<Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="50"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>

        <StackPanel Grid.Row="0">
            <Button Name="addItem" Width="50" Height="50" Content="AddItem"  HorizontalAlignment="Left" Click="addItem_Click"/>
        </StackPanel>

        <ListBox Grid.Row="1" ItemsSource="{Binding Source={StaticResource EmployeesSource}}"
         ItemTemplate="{StaticResource EmployeeTemplate}"
         SelectionMode="Extended">
            <ListBox.GroupStyle>
                <x:Static Member="GroupStyle.Default"/>
            </ListBox.GroupStyle>
        </ListBox>
</Grid>


[C# code]
public partial class Window1 : Window
{
        //public IEnumerable<Employee> Employees { get; set; }

        public ObservableCollection<Employee> Employees { get; set; }

        public Window1()
        {
            InitializeComponent();

            //初始化這邊可以加到UI上
            Employees = new ObservableCollection<Employee>
            {
                new Employee { FirstName = "FirstName1", LastName = "LastName1", HireDate = new DateTime(1970, 1, 1) },
                new Employee { FirstName = "FirstName2", LastName = "LastName2", HireDate = new DateTime(1970, 1, 1) },
                new Employee { FirstName = "FirstName3", LastName = "LastName3", HireDate = new DateTime(1980, 1, 1) },
                new Employee { FirstName = "FirstName4", LastName = "LastName4", HireDate = new DateTime(1980, 1, 1) },
                new Employee { FirstName = "FirstName5", LastName = "LastName5", HireDate = new DateTime(1980, 1, 1) },
                new Employee { FirstName = "FirstName6", LastName = "LastName6", HireDate = new DateTime(1990, 1, 1) },
                new Employee { FirstName = "FirstName7", LastName = "LastName7", HireDate = new DateTime(1990, 1, 1) },
                new Employee { FirstName = "FirstName8", LastName = "LastName8", HireDate = new DateTime(1990, 1, 1) },
                new Employee { FirstName = "FirstName9", LastName = "LastName9", HireDate = new DateTime(1990, 1, 1) },
            };
            DataContext = this;
        }

        private void addItem_Click(object sender, RoutedEventArgs e)
        {
        	//有增加進去, 但是UI不會新增這一筆1983的資料
            Employees.Add(new Employee {
                FirstName = "FirstName10",
                LastName = "LastName10",
                HireDate = new DateTime(1983, 1, 1)
            });
        }
}

class EmployeeCollectionView : ListCollectionView
{
        private readonly IList<EmployeeCollectionViewGroup> _groups;
        public override ReadOnlyObservableCollection<object> Groups
        {
            get { return new ReadOnlyObservableCollection<object>(new ObservableCollection<object>(_groups)); }
        }


        public EmployeeCollectionView(IList list)
            : base(list)
        {
            _groups = list
                 .OfType<Employee>()
                .GroupBy(x => x.HireDate)
                .Select(x => new EmployeeCollectionViewGroup(x.Key, x))
                .ToList();
        }


}

class EmployeeCollectionViewGroup : CollectionViewGroup
{
        public EmployeeCollectionViewGroup(object name, IEnumerable<object> protectedItems)
            : base(name)
        {
            foreach (var protectedItem in protectedItems)
                ProtectedItems.Add(protectedItem);
        }

        public override bool IsBottomLevel
        {
            get { return true; }
        }

        //新增屬性
        public bool IsDeleting { get; set; }
}

public class Employee : INotifyPropertyChanged
{
        public event PropertyChangedEventHandler PropertyChanged;
        private string m_FirstName;
        public string FirstName
        {
            get { return m_FirstName; }
            set
            {
                m_FirstName = value;
                if (PropertyChanged != null)
                    PropertyChanged(this, new PropertyChangedEventArgs("FirstName"));
            }

	}
        private string m_LastName;
        public string LastName
        {
            get { return m_LastName; }
            set
            {
                m_LastName = value;
                if (PropertyChanged != null)
                    PropertyChanged(this, new PropertyChangedEventArgs("LastName"));
            }
        }

        private DateTime m_HireDate;
        public DateTime HireDate
        {
            get { return m_HireDate; }
            set
            {
                m_HireDate = value;
                if (PropertyChanged != null)
                    PropertyChanged(this, new PropertyChangedEventArgs("HireDate"));
            }
        }

}