Well, SendKeys works by sending the key information to the _active_  
application.  This may or may not be your own.  It's whichever application  
is in the foreground with input focus.  You definitely can use SendKeys  
with a process other than your own.

You'd still need the unmanaged API to bring the media player to the  
foreground.  It's just that SendKeys allows you to treat the key  
information in a managed way.

If it's not appropriate for the media player to be the foreground, focused  
application when you send the key data to it, then SendKeys isn't what you  
want.

As for your original question: did you try those codes?  Do they work as  
you expect them to?  If so, I'd say you got it right.  If not, I'd say you  
got it wrong.

I haven't bothered to figure out the codes myself, but IMHO the docs are  
pretty clear on what should be sent.  For WM_KEYDOWN and WM_KEYUP you'll  
need to use the "VK" code for the P key in combination with the  
appropriate code for the control key in order to generate the Control-P.  
Note that by "in combination" I mean you need to generate the appropriate  
messages for both keys.

I'm actually a bit surprised that there's no automation API for the  
Windows Media Player.  I'm assuming you've looked for such an API and was  
unable to find it.  If not, you might want to look into that as well.  It  
might be easier to be able to create a new WMP process instance from your  
application that you can control directly rather than having to go through  
the unmanaged API.

Sorry I don't know more about it.  I was just trying to make sure you were  
aware of the SendKeys class, in case that's something that was useful for  
you.

Pete

WMP comes with an automation compatible object model, that means you can
control Media Player from any language that supports COM automation.
To use it from C#, you simply need to
- add a COM reference to "Windows Media Player" (wmp.dll),
- add a using directive like:
       using WMPLib;
and you can access the OM like this:
       WindowsMediaPlayer mediaPlayer = new WindowsMediaPlayerClass();
       mediaPlayer .openPlayer(@"someMediaFile");
       ....

Willy.