using System;

using System.Collections.Concurrent;

​

public class Program

{

    public static void Main()

    {

        // New instance.

        var con = new ConcurrentDictionary<string, int>();

        con.TryAdd("cat", 1);

        con.TryAdd("dog", 2);

        // Try to update if value is 4 (this fails).

        con.TryUpdate("cat", 200, 4);

        // Try to update if value is 1 (this works).

        con.TryUpdate("cat", 100, 1);

        // Write new value.

        Console.WriteLine(con["cat"]);

    }

}