using System;

using System.Collections;  

public class Program

{

    public static void Main()

    {

        //Console.WriteLine("Hello World");

        string[] Header;

        Header = new string[3]{"Element1","Element2","Element3"};

        ArrayList myArrayList = new ArrayList();

        myArrayList.AddRange(Header);

        int position=myArrayList.IndexOf("Element3"); 

        Console.WriteLine(position);

    }

}