C#

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

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            ArrList();
        }

        static void ArrList()
        {
            ArrayList Numbers = new ArrayList();
            Numbers.Add(7);
            Numbers.Add(7);
            Numbers.Add(5);

            foreach (int i in Numbers)
            {
                Console.WriteLine(i);
            }

            int IndexOfSeven = Numbers.IndexOf(7);
            Console.WriteLine("index is:" + IndexOfSeven);

            Console.ReadLine();
        }
    }

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

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            ArrList();
        }

        static void ArrList()
        {
            ArrayList Numbers = new ArrayList();
            Numbers.Add(7);
            Numbers.Add(7);
            Numbers.Add(5);

            foreach (int i in Numbers)
            {
                Console.WriteLine(i);
            }

            int IndexOfSeven = Numbers.IndexOf(7);
            Console.WriteLine("index is:" + IndexOfSeven);

            Console.ReadLine();
        }
    }

}