[C#] Parallel.Foreach

using System;
using System.Collections.Generic;
using System.Net;
using System.Threading.Tasks;

public class Proxy
{
  public IPAddress IP { get; set; }
  public string Hostname { get; set; }
}

public static class Test
{
  public static Dictionary<int,Proxy> Hosts = new Dictionary<int,Proxy>();
  public static void GetHostNames()
  {
    ParallelOptions popts = new ParallelOptions();
    popts.MaxDegreeOfParallelism = 256;
    Parallel.ForEach<int>(Hosts.Keys, popts, p =>
      {
        try
        {
          Hosts[p].Hostname = Dns.GetHostEntry(Hosts[p].IP).HostName;
        }
        catch 
        {
          Hosts[p].Hostname = "Error";
        }
      }
      );
  }
}

sectoid@nyarly:~ $ dmcs -t:library test.cs
sectoid@nyarly:~ $ dmcs --version
Mono C# compiler version 2.10.1.0

 struct Proxy
    {
        public IPAddress IP;
        public int Port;
        public string Hostname;
        public bool Alive;
        public bool Scanned;
    }