1    public class Chain<T> : IEnumerable<T>, IEnumerable
2    {
3        private static readonly Chain<T> empty = new Chain<T>(default(T), null);
4        public static Chain<T> Empty
5        {
6            get { return empty; }
7        }
8
9        public static Chain<T> From(T t)
10        {
11            return Empty.Append(t);
12        }
13
14        public static Chain<T> From(IEnumerable<T> _Items)
15        {
16            return Empty.Append(_Items);
17        }
18
19        public static Chain<T> From(params T[] items)
20        {
21            return Empty.Append(items);
22        }
23
24        private readonly T item;
25        private readonly Chain<T> next;
26
27        private IEnumerable<T> GetItemsRecursive()
28        {
29            if (next != null) {
30                foreach (T child in next.GetItemsRecursive()) yield return child;
31                yield return item;
32            }
33        }
34
35        public Chain<T> Append(T t)
36        {
37            return new Chain<T>(t, this);
38        }
39
40        public Chain<T> Append(IEnumerable<T> _Items)
41        {
42            if (_Items == null) throw new ArgumentNullException("Items");
43            Chain<T> current = this;
44            foreach (T cur in _Items) {
45                current = current.Append(cur);
46            }
47            return current;
48        }
49
50        public Chain<T> Append(params T[] items)
51        {
52            return Append((IEnumerable<T>) items);
53        }
54
55        private Chain(T _Item, Chain<T> _Next)
56        {
57            item = _Item;
58            next = _Next;
59        }
60
61        public IEnumerator<T> GetEnumerator()
62        {
63            return GetItemsRecursive().GetEnumerator();
64        }
65
66        IEnumerator IEnumerable.GetEnumerator()
67        {
68            return GetItemsRecursive().GetEnumerator();
69        }
70    }