using System;
using System.Runtime.InteropServices;
class Program {
   internal delegate bool DelegBeep(uint iFreq, uint iDuration);
   [DllImport("kernel32.dll")]
   internal static extern IntPtr LoadLibrary(String dllname);
   [DllImport("kernel32.dll")]
   internal static extern IntPtr GetProcAddress(IntPtr hModule, 
                                                String procName);
   static void Main() {
      IntPtr kernel32 = LoadLibrary( "Kernel32.dll" );
      IntPtr procBeep = GetProcAddress( kernel32, "Beep" );
      DelegBeep delegBeep = Marshal.GetDelegateForFunctionPointer( 
         procBeep , typeof( DelegBeep ) ) as DelegBeep;
      delegBeep(100,100);
   }
}