System Threading C# by API

using System;
using System.Threading;
class MainClass
{
    public static void Main()
    {
        int firstInt = 25;
        int secondInt = 80;
        Console.WriteLine("firstInt initial value = {0}", firstInt);
        Console.WriteLine("secondInt initial value = {0}", secondInt);
        Interlocked.CompareExchange(ref firstInt, 50, secondInt);
        Console.WriteLine("firstInt after CompareExchange = {0}", firstInt);
        Console.WriteLine("secondInt after CompareExchange = {0}", secondInt);
    }
}