list.Sort()

       class Comp : IComparer<int>

        {

            public int Compare(int x, int y)

            {

                return x.CompareTo(y);

            }

        }

        static void Main(string[] args)

        {

            List<int> list = new List<int>();

            list.Add(6);

            list.Add(4);

            list.Add(1);

            list.Add(2);

            list.Add(5);

            Comp comp = new Comp();

            list.Sort(comp);

            for (int i = 0; i < list.Count; i++)

            {

                Console.WriteLine(list[i]);

            }

            Console.ReadKey();

        }