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);

        // Add dog with value of 5 if it does NOT exist.

        // ... Otherwise, add one to its value.

        con.AddOrUpdate("dog", 5, (k, v) => v + 1);

        // Display dog value.

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

        // Get mouse or add it with value of 4.

        int mouse = con.GetOrAdd("mouse", 4);

        Console.WriteLine(mouse);

        // Get mouse or add it with value of 660.

        mouse = con.GetOrAdd("mouse", 660);

        Console.WriteLine(mouse);

    }

}