RadListBox provides rich client-side API for manipulating the items. You can add,
remove, disable, reorder and transfer items.
Insert items
var item = new Telerik.Web.UI.RadListBoxItem();
item.set_text("Item Text");
listBox.get_items().add(item);
Delete items
var item = listBox.getItem(0);
listBox.get_items().remove(item);
Reorder items
var item = listBox.getItem(0);
var index = item.get_index();
listBox.reorderItem(item, index - 1);
Transfer items
//Transfer from source to destination
var item = listBoxSource.getItem(0);
listBoxSource.transferToDestination(item);
//Transfer from destination to source
var item = listBoxDestination.getItem(0);
listBox.transferFromDestination(item);
Disable items
var item = listBox.getItem(0);
item.disable();