c# - Wrong WParam value in IMessageFilter.PreFilterMessage -

i in process implement application-wide keyboard hook 1 of applications.
done using imessagefilter implementation overriding prefiltermessage method , adding imessagefilter main form.
far able test, of number , letter keys work without problem, when comes to, let's say, keys.left (code 37), wparam of message contains a, seems, wrong value (code 39).
, yes, did bit-and keys.keycode (which 65535 btw. means wouldn't matter).

if has idea or hint why works letter/number keys not keys.left highly appreciate that.

code:

public bool prefiltermessage(ref message m) {     if(m.msg == wm_keydown)     {         _keytable[(keys)m.wparam & keys.keycode] = true;     }      if(m.msg == wm_keyup)     {         _keytable[(keys)m.wparam & keys.keycode] = false;     }      return false; }