FindIndex() method

Question

1^st program is a List program, uses the FindIndex() method and it is executing well.

2^nd program is an Array program also uses FindIndex() method and it is  not executing. How to make it executing.

 1^st program

 using System;

using System.Collections.Generic;

class Program

{

    static void Main()

    {

        List<int> elements = new List<int>() { 10, 20, 31, 40 };

         int oddIndex = elements.FindIndex(x => x % 2 != 0);

        Console.WriteLine(oddIndex);//2

         Console.ReadKey();

    }

}

 2^nd program

 using System;

 class Program

{

    static void Main()

    {

        int[] array = { 15, 6, 7, 16 };

         int index = array.FindIndex(x => x == 6);

         Console.WriteLine("{0}", index);

         Console.ReadKey();

    }

}