var result = count1.Intersect(count2);

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

namespace ConsoleApp1
{
    class Programme2
    {
        static void Main(string[] args)
        {
//declare the two array variable count1 and count2 of the type string 
            string[] count1 = { "India", "Australia", "UK", "USA" };
            string[] count2 = { "India", "China", "UK", "China" };
/*apply the Intersect method on both of the array
 count1 and count2 and store the output in result variable*/
            var result = count1.Intersect(count2);
/*foreach loop will iterate over all the element of 
the variable item which store the output of the result variable*/ 
            foreach (var item in result)
            {
/*Console.WriteLine(item) print 
all element store in the item variable.*/
                Console.WriteLine(item);
            }
                Console.ReadLine();
        }
    }
}