Handlers for Commands and Control Notifications
The latest version of this topic can be found at Handlers for Commands and Control Notifications.
There are no default handlers for commands or control-notification messages. Therefore, you are bound only by convention in naming your handlers for these categories of messages. When you map the command or control notification to a handler, the Properties windows proposes a name based on the command ID or control-notification code. You can accept the proposed name, change it, or replace it.
Convention suggests that you name handlers in both categories for the user-interface object they represent. Thus a handler for the Cut command on the Edit menu might be named
afx_msg void OnEditCut();
Because the Cut command is so commonly implemented in applications, the framework predefines the command ID for the Cut command as ID_EDIT_CUT. For a list of all predefined command IDs, see the file AFXRES.H. For more information, see Standard Commands.
In addition, convention suggests a handler for the BN_CLICKED notification message from a button labeled "My Button" might be named
afx_msg void OnBnClickedMybutton();
You might assign this command an ID of IDC_MY_BUTTON because it is equivalent to an application-specific user-interface object.
Both categories of messages take no arguments and return no value.