Remove elements in a collection from SortedSet in CSharp

using System;//  ww  w  .  j  av a 2  s  . com
using System.Collections;
using System.Collections.Generic;
using System.IO;


class Program
{
    static void Main(string[] args)
    {
        SortedSet<string> set1 = new SortedSet<string>();
        set1.Add("a");
        set1.Add("b");
        set1.Add("d");
        set1.Add("d");
        
        SortedSet<string> set2 = new SortedSet<string>();
        set2.Add("a");
        set2.Add("b");
        set2.Add("c");
        set2.Add("d");
        
        set1.ExceptWith(set2);

        foreach (string s in set1)
        {
            Console.WriteLine(s);
        }


    }
}