using System;

using System.Collections.Concurrent;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        ConcurrentDictionary<String, String> context = new ConcurrentDictionary<String, String>();

        context.TryAdd("1","2");

        context.TryAdd("1","3");

        context.AddOrUpdate("1", "3", (key, oldValue) => "3" );

        context.AddOrUpdate("2", "3", (key, oldValue) => "3" );

        //Console.WriteLine(context));

        String t = "{ ";

        foreach (var display in context)

        {   

            t += display.Key;

            t += " : " + display.Value;

            t += ", ";

        }

        t.Substring(t.LastIndexOf(","));

        t += " }";

        Console.WriteLine(t);

    }

}