Using RegisterWindowMessage Defined Variable within Switch Statement

Posted on 2004-08-30
Medium Priority
Last Modified: 2013-12-03
I have been trying to use a RegisterWindowMessage defined variable within a switch statement expression, but my compiler keeps producing an error (i.e., case expression not  constant).  Can anyone tell me what I am doing wrong?  Here are my declarations for everything:

const UINT WM_WGMSG = RegisterWindowMessage (TEXT ("WG_Message"));

Within WndProc procedure:

switch (message) {
  case WM_WGMSG:
  return 1;


Finally, I am programming in C under Microsoft Visual Studio .net 2003.  
Question by:jtrades
  • 2
LVL 22

Assisted Solution

cookre earned 200 total points
ID: 11938438
Switch requires a compile time constants for its cases.  The value of your WM_WGMSG is not known until runtime.

Do you really need a system wide unique message code?

If it's just for use within your progrm(s), make up your own message code - some value above WM_USER (0x0400), say WM_USER+123.

If you must have system wide uniqueness, just add an explicit check for your message in the switch's 'default'.
LVL 48

Accepted Solution

AlexFM earned 800 total points
ID: 11938866
Agree with coorke about constant unknown at compile time.
However, RegisterWindowMessage is much better than constant messages. Just replace swithch with if - else if - ... else. If you want to use constant messages, use WM_APP and not WM_USER to prevent conflicts (Microsoft is already using some messages with values WM_USER + n).
LVL 22

Expert Comment

ID: 11938893
The nerve of them!  I've always taken that as sacrosanct.

Guess that's what I get for being lazxy.

Featured Post

Keep up with what's happening at Experts Exchange!

Sign up to receive Decoded, a new monthly digest with product updates, feature release info, continuing education opportunities, and more.

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

If you have ever found yourself doing a repetitive action with the mouse and keyboard, and if you have even a little programming experience, there is a good chance that you can use a text editor to whip together a sort of macro to automate the proce…
For most people, the WrapPanel seems like a magic when they switch from WinForms to WPF. Most of us will think that the code that is used to write a control like that would be difficult. However, most of the work is done by the WPF engine, and the W…
This is Part 3 in a 3-part series on Experts Exchange to discuss error handling in VBA code written for Excel. Part 1 of this series discussed basic error handling code using VBA. http://www.experts-exchange.com/videos/1478/Excel-Error-Handlin…
This video tutorial shows you the steps to go through to set up what I believe to be the best email app on the android platform to read Exchange mail.  Get the app on your phone: The first step is to make sure you have the Samsung Email app on your …

597 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question