Userdefined messages

In Borland Delphi (7) I can use user defined messages. I use them to let controls know when to update themselves. uses Messages; const MYCONTROLUPDATEMESSAGE = WM_USER + 123; // define a userdefined message If a certain action is triggered (I.e. I resize main form or change the visual style of the application) a message is being sent (broadcasted). And then all controls receive to notification and do what they do to respond (i.e. redraw themselves). So, is it possble in C# (to use userdefined messages) ? If yes then could I have a small example or link to a documentation ? Regards, Desmond