由于是调用API,所以必须导入命名空间
using System.Runtime.InteropServices;
using System.Text;
[DllImport( "winmm.dll", EntryPoint="mciSendStringA", CharSet=CharSet.Ansi )]
protected static extern int mciSendString( string lpstrCommand, StringBuilder lpstrReturnString, int uReturnLength, IntPtr hwndCallback );
private void btnOpenCD_Click(object sender, System.EventArgs e)

...{
mciSendString( "set cdaudio door open", null, 0, IntPtr.Zero );
}

private void btnCloseCD_Click(object sender, System.EventArgs e)

...{
mciSendString( "set cdaudio door closed", null, 0, IntPtr.Zero );
}