Close(X) button is not working in the dialog?

Hello.
You don't need to handle WM_CLOSE,
Did you overload a OnCancel()fuction?
If there isn't, you have to overload OnCancel() function and add this code

CDialog::OnCancel();

You can do as bellow.
First you create button named IDCANCEL.
and from IDCANCEL, define OnCancel()function.

Above mentioned solutions are answers to your question, i am just adding to it..

Whenever you start with a MFC Dialog based application.
You are given a dialog with two buttons OK & CANCEL.
Clicking either of them when your program is executed will exit the application.
Many times we don't need them & so we delete them, then the problem would be that your application will exit even on clicking a ENTER or ESC key from keyboard.

So you can do the following
1. Double click both the OK & CANCEL button, you will have two function created for ID_OK & ID_CANCEL (assumed to be Ids of your OK & CANCEL button).
2. Commenting OnOK() in the function created for ID_OK will prevent your application from exiting when an ENTER key is hit when your application is running.
3. In the function created for ID_CANCEL you can call a message box asking user whether to exit the application or not & based on the input act accordingly.

It always close the window unless you have artificially overridden this behavior or simply screwed up. I have no information to tell you how.

—SA

I've had this problem because I disabled the "cancel" button from the dialog window.