using System;

​

namespace Program

{

    public class Program

    {   

        public static void Main(string[] args)

        {

            var array = new int[]{5};

            ref int bar = ref Foo(array);

            Console.WriteLine(array[0]);            

            Console.WriteLine(bar);

            array[0] = 6;

            Console.WriteLine(array[0]);

            Console.WriteLine(bar);

            bar = 7;

            Console.WriteLine(array[0]);

            Console.WriteLine(bar);

        }

        static ref int Foo(int[] array){

            return ref array[0];

        }

    }

}

​