using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{   

    public class A

    {

        public IDictionary<int, IEnumerable<int>> D { get; set; }

        public IEnumerable<int> H { get; set; }

    }

    public static void Main()

    {

        var hashSet = new HashSet<int>{1,2,1};

        PrintCollection(hashSet);

        Console.WriteLine();        

        var a = new A { H = hashSet }; 

        PrintCollection(a.H);

        Console.WriteLine();        

        var d = new Dictionary<int, HashSet<int>>

        {

            { 3, hashSet  }

        };

        a.D = d;

        PrintCollection(a.D.First().Value);

        Console.WriteLine();        

    }

    public static void PrintCollection(IEnumerable<int> collections)

    {

        foreach (var item in collections)

            Console.WriteLine(item);

    }

}