using System;

using System.Collections.Generic;

using System.Linq;

​

namespace Small

{

    public class Program

    {

        public static void Main(string[] args)

        {

            List<string> lst = new List<string>{"abcXdef", "abcXdef", "abcede", "aYcde", "X"};

            List<string> num = new List<string>{"X", "Y", "Z"};

            var fin = lst.Intersect(num, new MiNumeroEqualityComparer()).ToList();

            Console.ReadLine();

        }

    }

​

    public class MiNumeroEqualityComparer : IEqualityComparer<string>

    {

        public bool Equals(string x, string y)

        {

            Console.WriteLine("Equals called for {0} and {1}.", x, y);

            return x.Contains(y);

        }

​

        public int GetHashCode(string obj)

        {

            Console.WriteLine("GetHashCode alled for {0}.", obj);

            return obj.GetHashCode();

        }

    }

}