C# Manual List Union; finds items in both lists and display distinct list

ListUnion.cs

  static void Union()
        {
            int[] first = new[] { 1, 2, 3, 4, 6, 7, 7, 8, 8, 75, 4, 4, 3, 3, 3, 3, 4, 56, 6, 7, 7, 6, 4, 3, 2, 35, 56, 56, 56, 5, 77 };
            int[] second = new[] { 1, 3, 5 };
            List<int> InBoth = new List<int>();

            for(var i = 0; i< first.Length; i++)
            {
                for(var v =0; v<second.Length; v++)
                {
                    if (first[i] == second[v])
                    {
                        bool canAdd = true;

                        foreach(var z in InBoth)
                        {
                            if (z == second[v])
                                canAdd = false;

                            if (!canAdd)
                                break;
                        }

                        if (canAdd)
                          InBoth.Add(first[i]);
                    }
                }
            }
            foreach(var b in InBoth)
            {
                Console.Write(b + " ");
            }
            Console.WriteLine();
        }