MFC catch Control's Message of child from parent without create class handler for child?

Question

I have a CDialog created by wizard named CDialogParent, then create a child dialog template has IDD= IDD_CHILD_DLG1, in this child dialog I put one button IDC_BTN1 (I don't create class handler for this child).

BOOL CDialogParent::OnInitDialog()
{
  ....
  CDialog *pChild = new CDialog();
  pChild->Create(IDD_CHILD_DLG1, this);
  pChild->ShowWindow(SW_NORMAL);
}

Normally, I need to create new class handler CDialogChild for child and add message map like:

BEGIN_MESSAGE_MAP(CDialogChild, CDialog)
      ON_BN_CLICKED(IDC_BTN1, &CDialogChild::OnBnClickedBtn1)
END_MESSAGE_MAP()

Problem that I want to catch control's message IDC_BTN1 of child dialog BUT by declare message map in CDialogParent like:

BEGIN_MESSAGE_MAP(CDialogParent, CDialog)
    ON_BN_CLICKED(IDC_BTN1, &CDialogParent::OnBnClickedBtn1)
END_MESSAGE_MAP()

How to do this without create new class handler? Thanks for help!

Answer 1

In short: You cannot.

There are 2 reasons why this is not possible:

1. Control IDs are unique among siblings (i.e. controls sharing the same parent window) only. Different dialogs can use the same ID for different controls.
2. I'll assume you mean Owned dialog when you say Child dialog (those are different concepts, but the following rationale is the same). When setting up an owner-owned window relationship, that relationship is based on window handles (HWND). There is no additional C++ type information available. Both the type and object pointer are required to call the appropriate class member in a message map.

If you want to be informed about an event raised in an owned dialog, implement a message handler in the owned dialog's class and post a message to the owning dialog.