C#中调用Windows API

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;

namespace BeepTest
{
    class Program
    {
        [DllImport("kernel32.dll")]
        public static extern bool Beep(int frequency, int duration);
        static void Main(string[] args)
        {
            Random random = new Random();
            for (int i=0; i < 10000; i++)
            {
                Beep(random.Next(10000), 100);
            }
        }
    }
}

还是不会用，c#调用WindowsAPI，怎样才算会，怎样才算懂