private class UserDefineType
        {
           private int index;
            private string name;
            public UserDefineType(int index, string name)
            {
                Index = index;
                Name = name;
            }
            public int Index { get { return index; }set { index = value; } }
            public string Name { get { return name; }set { name = value; } }
        }
        List<UserDefineType> udtInstance = new List<UserDefineType>() { new UserDefineType(2,"c"), new UserDefineType(2, "d"), new UserDefineType(3, "a"), new UserDefineType(3, "b"), new UserDefineType(1, "e") , new UserDefineType(1, "f") };

        private void SortUDTInstance()
        {
            List<UserDefineType> sortByIndex= udtInstance.OrderBy(udt => udt.Index).ToList();
            List<UserDefineType> sortByName= udtInstance.OrderBy(udt => udt.Name).ToList();
            List<UserDefineType> sortByIndexAndName= udtInstance.OrderBy(udt => udt.Index).ThenBy(udt => udt.Name).ToList();
            List<UserDefineType> descendingSortByIndex = udtInstance.OrderByDescending(udt => udt.Index).ToList();

        }

利用Lambda。