C#怎样打开关闭CDROM?

using System;
using System.Text;
using System.Runtime.InteropServices;

class CloseCD
{
    [DllImport( "winmm.dll", EntryPoint="mciSendStringA", CharSet=CharSet.Ansi )]
    protected static extern int mciSendString( string lpstrCommand, StringBuilder lpstrReturnString, int uReturnLength, IntPtr hwndCallback);

    public static void Main()
    {
        int ret = mciSendString( "set cdaudio door open", null, 0, IntPtr.Zero );
        Console.ReadLine();
        ret = mciSendString( "set cdaudio door closed", null, 0, IntPtr.Zero );
    }
}