Working with Dialog Boxes in MFC
During the life cycle of a dialog box, the user invokes the dialog box, typically inside a command handler that creates and initializes the dialog object, the user interacts with the dialog box, then dialog box closes.
For modal dialog boxes, your handler gathers any data the user entered once the dialog box closes. Since the dialog object exists after its dialog window has closed, you can simply use the member variables of your dialog class to extract the data.
For modeless dialog boxes, you may often extract data from the dialog object while the dialog box is still visible. At some point, the dialog object is destroyed; when this happens depends on your code.