using System;
using System.Linq;
public class Program
{
public static void Main()
var all = "first,second,third,forth";
var removed = "second,forth";
var r = all.Split(',')
.Except( removed.Split(',') )
.Aggregate( "", (s,a)=>s+","+a )
.Substring(1);
Console.WriteLine( r );
}
