this link(http://es.infragistics.com/community/blogs/devin_rader/archive/2011/06/01/using-behaviors-to-synchronize-selected-items-of-infragistics-silverlight-controls-to-a-viewmodel.aspx) shows how to synchronize multipleSelection from the UI side.

but if i initialize the SelectedCustomers property by adding two customer, run it, the UI side doesn't show the information.

now i can get the multipleSelection itmes' value by this following way,

1. define the SelectedItemsValues

        public static readonly DependencyProperty SelectedItemsValuesProperty = DependencyProperty.Register("SelectedItemsValues", typeof(List), typeof(XamComboEditorSelectedItemsBehavior), new PropertyMetadata(OnSelectedItemsPropertyChanged));
        public List SelectedItemsValues

2. in the  Combobox.SelectedItems.CollectionChanged event, foreach the items to get the value what i want. each item is ICityDimension type.

            UnsubscribeFromEvents();
            Transfer(Combobox.SelectedItems, SelectedItems as IList);
            List results= new List();
            foreach (object tmp in Combobox.SelectedItems)
            {
                convert.Add(((ICityDimension)val).Description);
            }
            SelectedItemsValues = convert;
            SubscribeToEvents();

anybody can tell me how to set the initial Display Text when the SelectedItems is from the DB side instead of user's UI selection,  or which property/evnet  related to Display the text? if possible, can give a demo(MVVM pattern)?thanks in advance.

my behavior class is as follows:::::

 public class XamComboEditorSelectedItemsBehavior : Behavior
    {
        private XamComboEditor Combobox
        {
            get
            {
                return AssociatedObject as XamComboEditor;
            }
        }

        public static readonly DependencyProperty SelectedItemsProperty = DependencyProperty.Register("SelectedItems", typeof(INotifyCollectionChanged), typeof(XamComboEditorSelectedItemsBehavior), new PropertyMetadata(OnSelectedItemsPropertyChanged));
        public INotifyCollectionChanged SelectedItems
        {
            get { return (INotifyCollectionChanged)GetValue(SelectedItemsProperty); }
            set { SetValue(SelectedItemsProperty, value); }
        }

        public static readonly DependencyProperty SelectedItemsValuesProperty = DependencyProperty.Register("SelectedItemsValues", typeof(List), typeof(XamComboEditorSelectedItemsBehavior), new PropertyMetadata(OnSelectedItemsPropertyChanged));
        public List SelectedItemsValues
        {
            get { return (List)this.GetValue(SelectedItemsValuesProperty); }
            set { this.SetValue(SelectedItemsValuesProperty, value); }
        }

        private static void OnSelectedItemsPropertyChanged(DependencyObject target, DependencyPropertyChangedEventArgs args)
        {
            var collection = args.NewValue as INotifyCollectionChanged;
            if (collection != null)
            {
                collection.CollectionChanged += ((XamComboEditorSelectedItemsBehavior)target).ContextSelectedItems_CollectionChanged;
            }
        }

        protected override void OnAttached()
        {
            base.OnAttached();

            Combobox.SelectedItems.CollectionChanged += new NotifyCollectionChangedEventHandler(SelectedItems_CollectionChanged);
            //Combobox.Loaded += new RoutedEventHandler(Combobox_Loaded);
      
        }

        void Combobox_Loaded(object sender, RoutedEventArgs e)
        {
            throw new NotImplementedException();
        }

        void ContextSelectedItems_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
        {
            UnsubscribeFromEvents();

            Transfer(SelectedItems as IList, Combobox.SelectedItems);

            SubscribeToEvents();
        }

        void SelectedItems_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
        {
            UnsubscribeFromEvents();
            Transfer(Combobox.SelectedItems, SelectedItems as IList);
            List convert = new List();
            foreach (object tmp in Combobox.SelectedItems)
            {
                convert.Add(((ICityDimension)tmp).Description);
            }
            SelectedItemsValues = convert;
            SubscribeToEvents();
        }

        private void SubscribeToEvents()
        {
            Combobox.SelectedItems.CollectionChanged += SelectedItems_CollectionChanged;

            if (SelectedItems != null)
            {
                SelectedItems.CollectionChanged += ContextSelectedItems_CollectionChanged;
            }
        }

        private void UnsubscribeFromEvents()
        {
            Combobox.SelectedItems.CollectionChanged -= SelectedItems_CollectionChanged;

            if (SelectedItems != null)
            {
                SelectedItems.CollectionChanged -= ContextSelectedItems_CollectionChanged;
            }
        }

        public static void Transfer(IList source, IList target)
        {
            if (source == null || target == null)
                return;

            target.Clear();

            foreach (var tmp in source)
            {
                target.Add(tmp);
            }
        }
    }