using System;       

using System.Collections.Generic;

​

​

public class Program

{

    public static void Main()

    {

       var strItems = new string[] { "4", "5" ,"1", "2", "3"};

         var strItems2 = new string[] { "4", "3"};

        string str="";

            var list = new List<string>(strItems);

          for (int i = 0; i < strItems2.Length; i++)

                {

                     list.Remove(strItems2[i]);

                }

      strItems = list.ToArray();

              for (int i = 0; i < strItems.Length; i++)

                {

                  str=str+strItems[i]+",";

                }

    Console.WriteLine(str);

    }

}