在对话框上创建子窗口成功，但不显示？

BOOL CMainForm::AXCreate(int index, CWnd *wnd, const RECT& rect)
{
    BOOL bl = FALSE;

    try
    {
        LPCTSTR clsname = AfxRegisterWndClass(CS_DBLCLKS);
        bl=Create(clsname, _T(""), WS_CHILD | WS_VISIBLE, rect, wnd, index);
        if (bl==FALSE)
        {
            AfxMessageBox(_T("CMainForm!"));
        }
        else
        {
        }
    }
    catch(...)
    {
        AfxMessageBox(_T("CMainForm error!"));
    }
    return bl;
}

BOOL CMainForm::CreateWin(int index, CWnd *wnd, const RECT &rect)
{
    BOOL bl = AXCreate(index, wnd, rect);        //创建一个子窗口


    CRect t;
    this->GetClientRect(&t);


    this->GetDC()->SetBkColor(RGB(255, 0, 0));

    return TRUE;
}