public void Start() { Console.WriteLine("============Except Demo============"); // initialize datas uint[] ids = createIDs(10); string idstr = ids[0].ToString(); for (int i = 1; i < ids.Length; i++) { idstr += " " + ids[i].ToString(); } // add KeyedList <uint, DemoItem> list = new KeyedList <uint, DemoItem>(); KeyedList <uint, DemoItem> subList = new KeyedList <uint, DemoItem>(); for (int i = 0; i < ids.Length; i++) { var item = new DemoItem(ids[i], $"Item_{ids[i]}"); list.Add(item); if (i < ids.Length / 2) { subList.Add(item); } } Console.WriteLine("Before Except:"); print(list); Console.WriteLine("Sub List:"); print(subList); Console.WriteLine("After Except"); list = KeyedList <uint, DemoItem> .Except(list, subList); print(list); }