using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var listboxItems = new List<string>() { "orange", "yellow", "blue", "red", "black", "brown", "white" };

        //Treffer erwartet

        var blackList1 = new List<string>() { "black", "white" };       

        if (listboxItems.Any(x => blackList1.Contains(x)))

        {

            Console.WriteLine("Blacklisted items found!");

        }

        else

        {

            Console.WriteLine("No matches!");

        }

        //keine Treffer erwartet

        var blackList2 = new List<string>() { "pink", "aubergine" };        

        if (listboxItems.Any(x => blackList2.Contains(x)))

        {

            Console.WriteLine("Blacklisted items found!");

        }

        else

        {

            Console.WriteLine("No matches!");

        }

    }

}