Class Inheritance

The key point that CMultiPageDHtmlDialog is better than CDHtmlDialog is that we can map DHTML events with same HTML element id to different handlers.

How to change

Replace CDHtmlDialog to CMultiPageDHtmlDialog, and it needs to change something.

In CMultiPageDHtmlDialog, Using DECLARE_DHTML_URL_EVENT_MAP instead of DECLARE_MESSAGE_MAP to map DHTML events to handlers.

Remarks

A multipage dialog displays multiple HTML pages sequentially and handles the events from each page. The mechanism for doing this is a DHTML and URL event map, which contains embedded event maps for each page.

Example

This multipage dialog assumes three HTML resources that define simple wizard-like functionality. The first page has a Next button, the second a Prev and Next button, and the third a Prev button. When one of the buttons is pressed, a handler function calls CDHtmlDialog::LoadFromResource.aspx) to load the appropriate new page.

The pertinent parts of the class declaration (in CMyMultiPageDlg.h):

class CMyMultiPageDlg : public CMultiPageDHtmlDialog
{
public:
   // Declare the DHTML event handlers:
   HRESULT OnPage1Next(IHTMLElement *pElement);
   HRESULT OnPage2Next(IHTMLElement *pElement);
   HRESULT OnPage2Back(IHTMLElement *pElement);
   HRESULT OnPage3Back(IHTMLElement *pElement);
...
   DECLARE_DHTML_URL_EVENT_MAP()
}

The pertinent parts of the class implementation (in CMyMultipageDlg.cpp):

BEGIN_DHTML_URL_EVENT_MAP(CMyMultiPageDlg)

   BEGIN_EMBED_DHTML_EVENT_MAP(CMyMultiPageDlg, Page1)
      DHTML_EVENT_ONCLICK(_T("Next"), OnPage1Next)
   END_EMBED_DHTML_EVENT_MAP()

   BEGIN_EMBED_DHTML_EVENT_MAP(CMyMultiPageDlg, Page2)
      DHTML_EVENT_ONCLICK(_T("Back"), OnPage2Back)
      DHTML_EVENT_ONCLICK(_T("Next"), OnPage2Next)
   END_EMBED_DHTML_EVENT_MAP()

   BEGIN_EMBED_DHTML_EVENT_MAP(CMyMultiPageDlg, Page3)
      DHTML_EVENT_ONCLICK(_T("Back"), OnPage3Back)
   END_EMBED_DHTML_EVENT_MAP()

   BEGIN_URL_ENTRIES(CMyMultiPageDlg)
      URL_EVENT_ENTRY(CMyMultiPageDlg, _T("131"), Page1)
      URL_EVENT_ENTRY(CMyMultiPageDlg, _T("132"), Page2)
      URL_EVENT_ENTRY(CMyMultiPageDlg, _T("133"), Page3)
      // Note: IDR_PAGE1 = 131, IDR_PAGE2 = 132, IDR_PAGE3 = 133
   END_URL_ENTRIES()

END_DHTML_URL_EVENT_MAP(CMyMultiPageDlg)

HRESULT CMyMultiPageDlg::OnPage1Next(IHTMLElement *pElement)
{
   LoadFromResource(IDR_PAGE2);
   return S_OK;
}

HRESULT CMyMultiPageDlg::OnPage2Next(IHTMLElement *pElement)
{
   LoadFromResource(IDR_PAGE3);
   return S_OK;
}

HRESULT CMyMultiPageDlg::OnPage2Back(IHTMLElement *pElement)
{
   LoadFromResource(IDR_PAGE1);
   return S_OK;
}

HRESULT CMyMultiPageDlg::OnPage3Back(IHTMLElement *pElement)
{
   LoadFromResource(IDR_PAGE2);
   return S_OK;
}

Reference : MSDN