using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Collections;  

public class Program

{

    public static void Main()

    {

        IList<string> strList1 = new List<string>() 

        { 

            "One", 

            "Two", 

            "Three", 

            "Four"

        };

​

        IList<string> strList2 = new List<string>() 

        { 

            "One", 

            "Two", 

            "Five", 

            "Six"

        };

​

        var innerJoin = strList1.Join(strList2,

            str1 => str1, 

            str2 => str2, 

            (str1, str2) => str1);

​

        foreach (var str in innerJoin)                  

            Console.WriteLine(str);     

    }

}