WPF listbox异步绑定数据IsAsync=True

 <Grid>        <ListBox                 ItemsSource="{Binding List,IsAsync=True, RelativeSource={RelativeSource Mode=FindAncestor,AncestorType={x:Type local:MainWindow}}}"                   Height="179" HorizontalAlignment="Left"  Name="listBox1"                  VerticalAlignment="Top" Width="135" />    </Grid>

 public MainWindow()        {            InitializeComponent();        }        private IList<string> _list;        public IList<string> List        {            get            {                System.Threading.Thread.Sleep(3000);                if (_list == null)                {                    _list = new List<string>();                    for (int i = 0; i < 100; i++)                    {                        _list.Add("item" + i);                    }                }                return _list;            }        }