using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
public static void Main()
IEnumerable<string> oldVersions = new List<string>
"Hello" ,
"World",
"Hello"
};
IEnumerable<string> newVersions= new List<string>{
"World"
var temp = oldVersions.Except(newVersions);
foreach (var item in temp){
Console.WriteLine(item);
}