int[]{5,9,3,2,0,8,7,1,9};

            int[] arr = { 5, 9, 3, 2, 0, 8, 7, 1, 9 };
            List<int> list = arr.OrderByDescending(x => x).Take(5).ToList<int>();
            arr.ToList().ForEach(x => { if (list.Contains(x))Console.WriteLine(x); });

------解决方案--------------------
C# code

  int[] int_array=new int[]{5,9,3,2,0,8,7,1,9};
                int_array=int_array.Select((a, i) => new { index = i, value = a }).OrderByDescending(a => a.value).Take(5).OrderBy(a => a.index).Select(a=>a.value).ToArray();

                /*
                        [0]    5    int
                        [1]    9    int
                        [2]    8    int
                        [3]    7    int
                        [4]    9    int

                 */