C / C++ / MFC

class CFileChooser : public CStatic
{
// Construction
public:
	CFileChooser();

// Attributes
public:
	#define ID_BASE_ID		((UINT)-1)
	enum { 
	  ID_DIR_DROP_BOX = (ID_BASE_ID - 1),	// current dir drop box control
	  ID_FILE_LIST_BOX = (ID_BASE_ID - 2),		// file list box control
	};

// Operations
public:

// Overrides
	// ClassWizard generated virtual function overrides
	//{{AFX_VIRTUAL(CFileChooser)
	public:
	virtual BOOL Create(DWORD dwStyle, const RECT& rect, CWnd* pParentWnd, UINT nID);
	protected:
	virtual void PreSubclassWindow();
	//}}AFX_VIRTUAL

// Implementation
public:
	virtual ~CFileChooser();

	// Generated message map functions
protected:
	void DoSizing();
	int CreateChildControls();
	CComboBox m_dirDropBox;
	CListBox m_fileListBox;
	//{{AFX_MSG(CFileChooser)
	afx_msg int OnCreate(LPCREATESTRUCT lpCreateStruct);
	afx_msg void OnSetFocus(CWnd* pOldWnd);
	afx_msg void OnShowWindow(BOOL bShow, UINT nStatus);
	afx_msg void OnEnable(BOOL bEnable);
	//}}AFX_MSG

	DECLARE_MESSAGE_MAP()
};

int CFileChooser::OnCreate(LPCREATESTRUCT lpCreateStruct) 
{
	if (CStatic::OnCreate(lpCreateStruct) == -1)
		return -1;

	if (!CreateChildControls())
		return -1;

	return 0;
}

void CFileChooser::PreSubclassWindow() 
{
	CStatic::PreSubclassWindow();
	SetWindowText(_T("FileChooser"));

	// remove edges used to locate control in resource editor
	// remove or modify this line if you really want the control
	// to have client or static edges
	ModifyStyleEx(WS_EX_STATICEDGE, 0);

	CreateChildControls();

	DoSizing();
}

int CFileChooser::CreateChildControls()
{
	if (m_dirDropBox.GetSafeHwnd() != NULL)
		return TRUE;  // already created controls

	CWnd* pParent = GetParent();
	if (pParent == NULL)
		return FALSE;

	// create child controls
	CRect rc(0, 0, 0, 0);

	// create the drop down box that holds the path tree
	if (!m_dirDropBox.Create(DW_DROP_STYLE, rc, pParent, ID_DIR_DROP_BOX))
		return FALSE;

	// create the file list box
	if (!m_fileListBox.Create(LBS_MULTIPLESEL|DW_LIST_STYLE, rc, pParent, ID_FILE_LIST_BOX))
		return FALSE;

	// get information for setting visibility/enable
	BOOL bEnable = IsWindowEnabled();
	BOOL bShow = (GetStyle() & WS_VISIBLE);
	
	// configure the directory drop box
	m_dirDropBox.EnableWindow(bEnable);
	m_dirDropBox.ShowWindow(bShow ? SW_SHOW : SW_HIDE);

	// configure the file list box	
	m_fileListBox.EnableWindow(bEnable);
	m_fileListBox.ShowWindow(bShow ? SW_SHOW : SW_HIDE);

	return TRUE;
}

void CFileChooser::DoSizing()
{
	// put child controls in the correct places
	if (m_dirDropBox.GetSafeHwnd() == NULL)
		return; // controls not yet created

	if (GetParent() == NULL)
		return;

	// get the size and position of this control
	CRect rc;
	GetWindowRect(&rc);
	GetParent()->ScreenToClient(&rc);

	// size the directory drop box
	m_dirDropBox.ShowWindow(GetStyle() & WS_VISIBLE ? SW_SHOW : SW_HIDE);
	m_dirDropBox.MoveWindow(rc.left, rc.top, rc.Width(), DROP_BOX_SIZE);

	// adjust the rect object rc to no longer include the area with
	// the drop box and the gap between the drop box and the list box
	rc.top += BOX_CTRL_GAP + DROP_BOX_SIZE;

	// put lists one either side beside buttons
	m_fileListBox.MoveWindow(rc.left, rc.top, rc.Width(), rc.Height());

	// redraw self and the controls
	RedrawWindow();
	m_dirDropBox.RedrawWindow();
	m_fileListBox.RedrawWindow();
}

CEdit
  A
  |
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CParsedEdit
  A
  |
  |
CParsedEditExport (for custom controls) 

CEdit   IEdit(abstract as interface)
  A     A
  |    /
  |   /
CParsedEdit
  A
  |
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CParsedEditExport (for custom controls) 

class IEdit {
public:
        virtual void setText(TCHAR* text)=0;
	virtual int getText(TCHAR* text, int count)=0;
};


class CParsedEdit : public IEdit, public CEdit {
public:
	virtual void setText(TCHAR* text) { SetWindowText(text); }
	virtual int getText(TCHAR* text, int count) { return GetWindowText(text, count); }
protected:
....
};

class CWclsEditDlg : public CDialog {
public:
	IEdit*  Edit1()
				{ return dynamic_cast<IEdit*>(GetDlgItem(IDC_EDIT1)); }
	IEdit*  Edit2()
				{ return dynamic_cast<IEdit*>(GetDlgItem(IDC_EDIT2)); }
	IEdit*  Edit3()
				{ return dynamic_cast<IEdit*>(GetDlgItem(IDC_EDIT3)); }
	IEdit*  Edit4()
				{ return dynamic_cast<IEdit*>(GetDlgItem(IDC_EDIT4)); }
....
};