using System;

using System.Linq;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        int[] numbers = {1, 5, 5, 6, 7, 8, 9, 9};

        Console.WriteLine(string.Join(",", numbers));

        //Console.WriteLine(string.Join(",", numbers.Distinct()));

        RemoveDuplicates(numbers);

    }

​

    public static void RemoveDuplicates(int[] numbers)

    {

        List<int> uniqueValues = new List<int>{numbers[0]};

        for(int i = 1; i < numbers.Length; i++)

        {

            if(!uniqueValues.Contains(numbers[i]))

               uniqueValues.Add(numbers[i]);

        }

        Console.WriteLine(string.Join(",", uniqueValues));

    }

}