How to Access a Subclassed Windows Control in an OLE Control

WINDOWS        | WINDOWS NT

The information in this article applies to:

• The Microsoft Foundation Classes (MFC) included with: Microsoft OLE Control Developer's Kit (CDK) versions 1.0, 1.1, 1.2

SUMMARY

The ControlWizard provided with the CDK allows a new OLE control to be created by subclassing a common Windows control such as a button, toolbar, or edit box. The XLIST sample provided with the CDK illustrates how to do this by subclassing a Windows list box. The XLIST sample communicates with and manipulates the subclassed Windows control by using the Windows SendMessage() API. For example, to insert a string into the subclassed list box, use this code:

   SendMessage(LB_INSERTSTRING, nIndex, (long)lpstrText);

MORE INFORMATION

The following sample code illustrates how to use the MFC CListBox class to communicate with a Windows list box control subclassed by an OLE control. The process for doing this is as follows:

1. Add a member variable of type CListBox to the declaration of the COleControl derived class:

   class CSubclassCtrl : public COleControl { ...

      // Implementation
      protected:
   
        CListBox  m_ListBox;
      ...
      }
   
   

2. Override the OnCreate member of the COleControl derived class and initialize the m_hWnd member of the CListBox member:

      int CSubclassCtrl::OnCreate(LPCREATESTRUCT lpCreateStruct)
      {
      if (COleControl::OnCreate(lpCreateStruct) == -1)
      return -1;
   
      m_ListBox.m_hWnd = m_hWnd;
   
        // Additional list box initialization can go here.
   
      return 0;
      }
   
   

3. Set the m_hWnd member of the CListBox member to NULL in the destructor of the COleControl derived class:

   CSubclassCtrl::~CSubclassCtrl() {

        m_ListBox.m_hWnd = NULL;
   

   }

   m_ListBox.InsertString(nIndex, _T("A String"));