using System;
using System.Collections.Generic;
public class TestList
{
    public static void Main()
    {
            List<int> aa = new List<int>();
            for (int i = 0; i <10; i++)
            {
                aa.Add(i);// 0,1, 2, 3, 4, 5, 6, 7, 8, 9;
            }
            List<int> bb = new List<int>();
            Test(aa, bb);
            foreach(int i in bb)
        {
            Console.WriteLine(i);
        }
            Console.ReadLine();
    }
        public static void Test(List<int> aa, List<int> bb)
        {
            if (aa.Count == 0) return;
            Random ra = new Random();
            int a = ra.Next(aa.Count);
            bb.Add(aa[a]);
            for (int i = 0; i < aa.Count; i++)
            {
                if (aa[i] == aa[a])
                {
                    aa.RemoveAt(i);
                }
            }
            Test(aa, bb);
        }
};