using System;

using System.Linq;

using System.Collections.Concurrent;

using System.Threading.Tasks;

using System.Threading;

​

public class Program

{

    public static void Main()

    {

        var bag = new ConcurrentBag<string>();

        Parallel.For(0, 100, (i, loopState) =>

        {

            bag.Add(GetUniqueId());

        }

​

        );

        Console.WriteLine(bag.ToArray().Distinct().Count());

    }

​

    private static string GetUniqueId()

    {

        return Thread.CurrentThread.ManagedThreadId + DateTime.UtcNow.Ticks.ToString().Substring(6);

    }

}