SoftwareEngineering2/ConsoleAppLock/ConsoleAppLock/Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleAppLock
{
    class Program
    {
        private static List<int> intlist;
        private static object lockobject;

        static void Main(string[] args)
        {
            intlist = new List<int>();
            lockobject = new object();

            containsNumber(5);
            addNumber(8);

            Console.Read();
        }

        static void containsNumber(int i)
        {
            if (!intlist.Contains(i))
            {
                intlist.Add(i);
            }
        }

        static void addNumber(int i)
        {
            intlist.Add(i);
        }
    }
}