With The Case Of  Release The Power OF  Visual C++ !   HomeProducts | PurchaseSupport | Downloads  
Download Evaluation
Pricing & Purchase?
E-XD++Visual C++/ MFC Products
Features Tour 
Electronic Form Solution
Visualization & HMI Solution
Power system HMI Solution
CAD Drawing and Printing Solution

Bar code labeling Solution
Workflow Solution

Coal industry HMI Solution
Instrumentation Gauge Solution

Report Printing Solution
Graphical modeling Solution
GIS mapping solution

Visio graphics solution
Industrial control SCADA &HMI Solution
BPM business process Solution

Industrial monitoring Solution
Flowchart and diagramming Solution
Organization Diagram Solution

Graphic editor Source Code
UML drawing editor Source Code
Map Diagramming Solution

Architectural Graphic Drawing Solution
Request Evaluation
ActiveX COM Products
Technical Support
  General Q & A
Discussion Board
Contact Us


Get Ready to Unleash the Power of UCanCode .NET


UCanCode Software focuses on general application software development. We provide complete solution for developers. No matter you want to develop a simple database workflow application, or an large flow/diagram based system, our product will provide a complete solution for you. Our product had been used by hundreds of top companies around the world!

"100% source code provided! Free you from not daring to use components because of unable to master the key technology of components!"

Visual C++ CComboBox: Auto-complete ComboBox

Chris Maunder
September 11, 1998 

Visual C++ 6.0, VC++ 2003, VC++ 2005

Download sample project and source files

I had a need for a combobox that would auto-complete, very much like the URL edit box in the toolbar of Netscape Navigator. It was actually surprisingly simple since the base CComboBox is so rich in functionality.

The basic idea is that every time the text in the edit box changes, check to see if there is any text in the drop down list that is prefixed by this edit box text. Handle the CBN_EDITUPDATE message to get the text change notifications, and use GetWindowText() to get the text. CComboBox::SelectString will look for a string in the list which is prefixed by the given string, and select it into the edit box. I then select the portion of text that was added to the users typed text so that they can continue typing and have the additions ignored if they wish. That takes care of 90% of the work.

The only trick is in handling backspaces and deletes. When a user hits delete, the text is changed, and the auto-completion routine will try to restore that text back again. Just check in PreTranslateMessage for a KEY_DOWN message with a virtual key of VK_DELETE or VK_BACK, and temporarily disable the auto-complete mechanism for those key strokes.

Source code

#if !defined(AFX_COMBOBOXEX_H__115F422E_5CD5_11D1_ABBA_00A0243D1382__INCLUDED_)
#define AFX_COMBOBOXEX_H__115F422E_5CD5_11D1_ABBA_00A0243D1382__INCLUDED_

#if _MSC_VER >= 1000
#pragma once
#endif // _MSC_VER >= 1000

// ComboBoxEx.h : header file
// Copyright (c) Chris Maunder 1997.
// Please feel free to use and distribute.

// CComboBoxEx window

class CComboBoxEx : public CComboBox
// Construction

// Attributes

// Operations

// Overrides
	// ClassWizard generated virtual function overrides
	virtual BOOL PreTranslateMessage(MSG* pMsg);

// Implementation
	virtual ~CComboBoxEx();

	BOOL m_bAutoComplete;

	// Generated message map functions
	afx_msg void OnEditUpdate();



// Microsoft Developer Studio will insert additional declarations immediately before the previous line.

#endif // !defined(AFX_COMBOBOXEX_H__115F422E_5CD5_11D1_ABBA_00A0243D1382__INCLUDED_)

// ComboBoxEx.cpp : implementation file
// Copyright (c) Chris Maunder 1997.
// Please feel free to use and distribute.

#include "stdafx.h"
#include "ComboBoxEx.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;

// CComboBoxEx

	m_bAutoComplete = TRUE;



// CComboBoxEx message handlers

BOOL CComboBoxEx::PreTranslateMessage(MSG* pMsg)
	// Need to check for backspace/delete. These will modify the text in
	// the edit box, causing the auto complete to just add back the text
	// the user has just tried to delete. 

	if (pMsg->message == WM_KEYDOWN)
		m_bAutoComplete = TRUE;

		int nVirtKey = (int) pMsg->wParam;
		if (nVirtKey == VK_DELETE || nVirtKey == VK_BACK)
			m_bAutoComplete = FALSE;

	return CComboBox::PreTranslateMessage(pMsg);

  // if we are not to auto update the text, get outta here
  if (!m_bAutoComplete)

  // Get the text in the edit box
  CString str;
  int nLength = str.GetLength();

  // Currently selected range
  DWORD dwCurSel = GetEditSel();
  WORD dStart = LOWORD(dwCurSel);
  WORD dEnd   = HIWORD(dwCurSel);

  // Search for, and select in, and string in the combo box that is prefixed
  // by the text in the edit box
  if (SelectString(-1, str) == CB_ERR)
      SetWindowText(str);		// No text selected, so restore what was there before
      if (dwCurSel != CB_ERR)
        SetEditSel(dStart, dEnd);	//restore cursor postion

  // Set the text selection as the additional text that we have added
  if (dEnd < nLength && dwCurSel != CB_ERR)
      SetEditSel(dStart, dEnd);
      SetEditSel(nLength, -1);



Copyright ?1998-2009 UCanCode.Net Software , all rights reserved.
Other product and company names herein may be the trademarks of their respective owners.

Please direct your questions or comments to