经过两天的编码调试，完成了一个自动过滤选择的组合框，具有以下优点：
1。丝毫不妨碍组合框原有的功能
2。根据用户在编辑框里已经输入的单词，从组合框的列表选项过滤出匹配的项，并使用下拉列表显示出来以供用户选择。
3。不需要特别的设置。从View\ClassWizard\Member Variables里生成一个CComboBox，然后在源文件里把CComboBox替换成CACComboBox即可；或者让ClassWizard认识CACComboBox(删除MyApp.clw，选View\ClassWizard，按提示重新生成MyApp.clw，绝大多数时候能成功)，从View\ClassWizard\Member Variables里直接生成一个CACComboBox。
4。你可以经过简单修改使之成为具有其他类似功能(自动填写？？)的组合框。

由于时间仓促，没有写详细的注释。感兴趣的朋友请等几天后向我索要。联系方法：
linger0822@163.net

代码如下：

file://-----------------------------------------------------------------------------
// File: ACComboBox.h
//
// Desc:
//   根据用户在编辑框里已经输入的单词，从组合框的列表选项过滤出匹配的项，并使用下拉列表显示出来以供用户选择
//
// Copyright (c) 2001 EagleFly Studio.
//
// Original Author: Zhengpeng.Lan
// Author:
//
// Create Time:  2001/10/10
// Modify Time:  2001/10/11
//
file://-----------------------------------------------------------------------------
#if !defined(AFX_ACCOMBOBOX_H__81CBBD04_3955_4076_A688_74D3EA9730D9__INCLUDED_)
#define AFX_ACCOMBOBOX_H__81CBBD04_3955_4076_A688_74D3EA9730D9__INCLUDED_

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

#include "afxtempl.h"

// ACComboBox.h : header file
//
class CACComboBox;
/////////////////////////////////////////////////////////////////////////////
// CWndForACComboBox window
typedef struct
{
int nid;
CString strDepict;
}CInfoForACComboBox;

typedef CArray<CInfoForACComboBox,CInfoForACComboBox &>  CInfoForACComboBoxArray;

class CWndForACComboBox : public CWnd
{
friend CACComboBox;
private:
// Construction
LPCTSTR lpWndCls;
// Construction
public:
CWndForACComboBox();

// Attributes
public:
CComboBox * m_pComboBox;
int   m_nMaxCount;
CInfoForACComboBoxArray   m_aInfo;
int   m_nMousePos;
int   m_nBeginShow;

inline void RemoveAll()
{
  m_aInfo.RemoveAll();
  CWnd::SetScrollRange(SB_VERT,0,0);
}
inline void Add(CInfoForACComboBox &info)
{
  m_aInfo.Add(info);
}
inline int GetSize()
{
  return m_aInfo.GetSize();
}
inline void ShowList()
{
  if(IsWindow(GetSafeHwnd()))
  {
   ShowWindow(SW_SHOWNOACTIVATE);
  }
}
// Operations
public:

// Overrides
// ClassWizard generated virtual function overrides
file://{{AFX_VIRTUAL(CWndForACComboBox)
public:
virtual BOOL Create(CComboBox * pWnd);
file://}}AFX_VIRTUAL

// Implementation
public:
virtual ~CWndForACComboBox();

// Generated message map functions
protected:
file://{{AFX_MSG(CWndForACComboBox)
afx_msg void OnDestroy();
afx_msg void OnPaint();
afx_msg void OnKeyDown(UINT nChar, UINT nRepCnt, UINT nFlags);
afx_msg void OnLButtonUp(UINT nFlags, CPoint point);
afx_msg BOOL OnMouseWheel(UINT nFlags, short zDelta, CPoint pt);
afx_msg void OnKillFocus(CWnd* pNewWnd);
afx_msg void OnMouseMove(UINT nFlags, CPoint point);
afx_msg void OnVScroll(UINT nSBCode, UINT nPos, CScrollBar* pScrollBar);
file://}}AFX_MSG
DECLARE_MESSAGE_MAP()
};


/////////////////////////////////////////////////////////////////////////////
// CACComboBox window

class CACComboBox : public CComboBox
{
private:
CEdit*      m_pEdit;

// Construction
public:
CACComboBox();

// Attributes
public:
CWndForACComboBox  m_wndList;
inline void WindowMove(void)
{
  if(IsWindow(m_wndList.GetSafeHwnd()))
   m_wndList.Invalidate(FALSE);
}
// Operations
public:
  virtual void HandleCompletion();

// Overrides
// ClassWizard generated virtual function overrides
file://{{AFX_VIRTUAL(CACComboBox)
protected:
virtual BOOL OnCommand(WPARAM wParam, LPARAM lParam);
virtual void PreSubclassWindow();
file://}}AFX_VIRTUAL

// Implementation
public:
virtual ~CACComboBox();

// Generated message map functions
protected:
file://{{AFX_MSG(CACComboBox)
afx_msg void OnKillfocus();
afx_msg void OnSelchange();
file://}}AFX_MSG

DECLARE_MESSAGE_MAP()
};

/////////////////////////////////////////////////////////////////////////////

/////////////////////////////////////////////////////////////////////////////
file://{{AFX_INSERT_LOCATION}}
// Microsoft Visual C++ will insert additional declarations immediately before the previous line.

#endif // !defined(AFX_ACCOMBOBOX_H__81CBBD04_3955_4076_A688_74D3EA9730D9__INCLUDED_)


file://-----------------------------------------------------------------------------
// File: ACComboBox.cpp
//
// Desc:
//   根据用户在编辑框里已经输入的单词，从组合框的列表选项过滤出匹配的项，并使用下拉列表显示出来以供用户选择
//
// Copyright (c) 2001 EagleFly Studio.
//
// Original Author: Zhengpeng.Lan
// Author:
//
// Create Time:  2001/10/10
// Modify Time:  2001/10/11
//
file://-----------------------------------------------------------------------------

#include "stdafx.h"
#include "ACComboBox.h"

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

/////////////////////////////////////////////////////////////////////////////
// CACComboBox

CACComboBox::CACComboBox()
:CComboBox()
{
m_pEdit = NULL;
}

CACComboBox::~CACComboBox()
{
if(m_pEdit)
  delete m_pEdit;
}


BEGIN_MESSAGE_MAP(CACComboBox, CComboBox)
file://{{AFX_MSG_MAP(CACComboBox)
ON_CONTROL_REFLECT(CBN_KILLFOCUS, OnKillfocus)
ON_CONTROL_REFLECT(CBN_SELCHANGE, OnSelchange)
file://}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CACComboBox message handlers
/////////////////////////////////////////////////////////////////////////////
// CWndForACComboBox

CWndForACComboBox::CWndForACComboBox()
:CWnd()
{
lpWndCls = AfxRegisterWndClass(0);
m_pComboBox = NULL;
m_nMaxCount = 8;
m_aInfo.SetSize(0,8);
m_nMousePos = -1;
m_nBeginShow = 0;
}

CWndForACComboBox::~CWndForACComboBox()
{

}


BEGIN_MESSAGE_MAP(CWndForACComboBox, CWnd)
file://{{AFX_MSG_MAP(CWndForACComboBox)
ON_WM_DESTROY()
ON_WM_PAINT()
ON_WM_KEYDOWN()
ON_WM_LBUTTONUP()
ON_WM_MOUSEWHEEL()
ON_WM_KILLFOCUS()
ON_WM_MOUSEMOVE()
ON_WM_VSCROLL()
file://}}AFX_MSG_MAP
END_MESSAGE_MAP()


/////////////////////////////////////////////////////////////////////////////
// CWndForACComboBox message handlers

BOOL CWndForACComboBox::Create(CComboBox * pWnd)
{
ASSERT(pWnd);

CRect rect;
CWnd * pParentWnd = pWnd->GetParent();

pWnd->GetWindowRect(&rect);
// pParentWnd->ScreenToClient(&rect);

BOOL bRet = CWnd::CreateEx( WS_EX_TOPMOST | WS_EX_TOOLWINDOW,\
  lpWndCls, NULL, WS_POPUP | WS_VSCROLL, rect.left, rect.top, rect.Width(), rect.Height(),
  pParentWnd->GetSafeHwnd(), NULL, NULL);

if(bRet)
  SetOwner(pParentWnd);

m_pComboBox = pWnd;
return bRet;
}

void CWndForACComboBox::OnDestroy()
{
CWnd::OnDestroy();

m_aInfo.RemoveAll();
}

void CWndForACComboBox::OnPaint()
{
CRect rect;
CFont * pFont;
LOGFONT logFont;

if(m_pComboBox)
{
  ASSERT(::IsWindow(m_pComboBox->GetSafeHwnd()));

  CWnd * pParentWnd = m_pComboBox->GetParent();
  m_pComboBox->GetWindowRect(&rect);
  pFont = pParentWnd->GetFont();
  ASSERT(pFont);
  pFont->GetLogFont(&logFont);

  if(logFont.lfHeight < 0) logFont.lfHeight = -logFont.lfHeight;
  if(m_aInfo.GetSize() > m_nMaxCount)
  {
   logFont.lfWidth = m_nMaxCount * logFont.lfHeight;
  }
  else
  {
   logFont.lfWidth = m_aInfo.GetSize() * logFont.lfHeight;
  }
  if(logFont.lfWidth + rect.bottom > ::GetSystemMetrics(SM_CYSCREEN))
  {
   rect.bottom = rect.top;
   rect.top = rect.bottom - logFont.lfWidth - 2;
   if(rect.top < 0)
    rect.top = 0;
  }
  else
  {
   rect.top = rect.bottom;
   rect.bottom = rect.top + logFont.lfWidth + 2;
  }
  rect.right = rect.left + m_pComboBox->GetDroppedWidth();
//  pParentWnd->ScreenToClient(&rect);
  MoveWindow(&rect);
  if(rect.Height() < m_aInfo.GetSize() * logFont.lfHeight)
  {
   TRACE("%d   %d\r\n",rect.Height(),m_aInfo.GetSize() * logFont.lfHeight);
   SCROLLINFO info;

   info.cbSize = sizeof(info);
   info.fMask = SIF_PAGE;
   info.nPage = rect.Height() / logFont.lfHeight;
   CWnd::SetScrollRange(SB_VERT,0,m_aInfo.GetSize() - 1,FALSE);
   CWnd::ShowScrollBar(SB_VERT,TRUE);
   CWnd::SetScrollInfo(SB_VERT,&info);
  }
  else
  {
   CWnd::ShowScrollBar(SB_VERT,FALSE);
  }
}
CPaintDC dc(this); // device context for painting

file://dc.FillSolidRect(0,0,rect.Width(),rect.Height(),RGB(255,255,255));
dc.Rectangle(0,0,rect.Width(),rect.Height());
logFont.lfWidth = 1;
dc.SelectObject(pFont);
int m_nBeginShow = CWnd::GetScrollPos(SB_VERT);
for(int i=m_nBeginShow;i<m_aInfo.GetSize() && logFont.lfWidth < rect.Height() - 2;i++)
{
  if(i == m_nMousePos)
  {
   dc.SetBkColor(RGB(0,0,128));
   dc.FillSolidRect(1,logFont.lfWidth,rect.Width() - 2,logFont.lfHeight,RGB(0,0,128));
   dc.SetTextColor(RGB(255,255,255));
  }
  else
  {
   dc.SetBkColor(RGB(255,255,255));
   dc.SetTextColor(RGB(0,0,0));
  }
  dc.TextOut(3,logFont.lfWidth,m_aInfo[i].strDepict);
  logFont.lfWidth += logFont.lfHeight;
}
}

void CWndForACComboBox::OnKeyDown(UINT nChar, UINT nRepCnt, UINT nFlags)
{
// TODO: Add your message handler code here and/or call default

CWnd::OnKeyDown(nChar, nRepCnt, nFlags);
}

void CWndForACComboBox::OnLButtonUp(UINT nFlags, CPoint point)
{
CFont * pFont;
LOGFONT logFont;

if(m_pComboBox)
{
  pFont = m_pComboBox->GetParent()->GetFont();
  pFont->GetLogFont(&logFont);
  if(logFont.lfHeight < 0) logFont.lfHeight = -logFont.lfHeight;
  m_nMousePos = (point.y - 1) / logFont.lfHeight + CWnd::GetScrollPos(SB_VERT);
  if(m_nMousePos >= 0 && m_nMousePos < m_aInfo.GetSize())
   m_pComboBox->SetCurSel(m_aInfo[m_nMousePos].nid);
  ShowWindow(SW_HIDE);
}

CWnd::OnLButtonUp(nFlags, point);
}

BOOL CWndForACComboBox::OnMouseWheel(UINT nFlags, short zDelta, CPoint pt)
{
// TODO: Add your message handler code here and/or call default

return CWnd::OnMouseWheel(nFlags, zDelta, pt);
}

void CWndForACComboBox::OnKillFocus(CWnd* pNewWnd)
{
CWnd::OnKillFocus(pNewWnd);

if(pNewWnd->GetSafeHwnd() != m_pComboBox->GetSafeHwnd() && pNewWnd->GetSafeHwnd() != GetSafeHwnd() && IsWindow(GetSafeHwnd()))
  ShowWindow(SW_HIDE);
}

void CWndForACComboBox::OnMouseMove(UINT nFlags, CPoint point)
{
CFont * pFont;
LOGFONT logFont;
::ShowCursor(TRUE);
if(m_pComboBox)
{
  pFont = m_pComboBox->GetParent()->GetFont();
  pFont->GetLogFont(&logFont);
  if(logFont.lfHeight < 0) logFont.lfHeight = -logFont.lfHeight;
  logFont.lfWidth = point.y / logFont.lfHeight + CWnd::GetScrollPos(SB_VERT);
  if(logFont.lfWidth != m_nMousePos)
  {
   m_nMousePos = logFont.lfWidth;
   Invalidate();
  }
}

CWnd::OnMouseMove(nFlags, point);
}

void CWndForACComboBox::OnVScroll(UINT nSBCode, UINT nPos, CScrollBar* pScrollBar)
{
if(m_aInfo.GetSize() <= 0)
{
  CWnd::OnVScroll(nSBCode, nPos, pScrollBar);
  return ;
}

switch(nSBCode)
{
// case SB_BOTTOM://Scroll to bottom.
// case SB_ENDSCROLL://End scroll.
case SB_LINEDOWN://Scroll one line down.
  {
   RECT rc;
   LOGFONT logFont;
   CFont * pFont;

   GetClientRect(&rc);
   pFont = m_pComboBox->GetParent()->GetFont();
   pFont->GetLogFont(&logFont);
   ASSERT(logFont.lfHeight != 0);
   if(logFont.lfHeight < 0) logFont.lfHeight = -logFont.lfHeight;
   rc.left = (rc.bottom - rc.top) / logFont.lfHeight;

   int nPos = GetScrollPos(SB_VERT) + 1;
   if(nPos + rc.left <= m_aInfo.GetSize())
   {
    SetScrollPos(SB_VERT,nPos);
    Invalidate();
   }
  }
  break;
case SB_LINEUP://Scroll one line up.
  {
   int nPos = GetScrollPos(SB_VERT) - 1;
   if(nPos >= 0)
   {
    SetScrollPos(SB_VERT,nPos);
    Invalidate();
   }
  }
  break;
case SB_PAGEDOWN://Scroll one page down.
  {
   RECT rc;
   LOGFONT logFont;
   CFont * pFont;

   GetClientRect(&rc);
   pFont = m_pComboBox->GetParent()->GetFont();
   pFont->GetLogFont(&logFont);
   ASSERT(logFont.lfHeight != 0);
   if(logFont.lfHeight < 0) logFont.lfHeight = -logFont.lfHeight;

   rc.top = rc.bottom / logFont.lfHeight;
   int nPos = GetScrollPos(SB_VERT);
   if(nPos < m_aInfo.GetSize() - rc.top)
   {
    nPos += rc.top;
    if(nPos > m_aInfo.GetSize() - rc.top) nPos = m_aInfo.GetSize() - rc.top;
    SetScrollPos(SB_VERT,nPos);
    Invalidate();
   }
  }
  break;
case SB_PAGEUP://Scroll one page up.
  {
   RECT rc;
   LOGFONT logFont;
   CFont * pFont;

   GetClientRect(&rc);
   pFont = m_pComboBox->GetParent()->GetFont();
   pFont->GetLogFont(&logFont);
   ASSERT(logFont.lfHeight != 0);
   if(logFont.lfHeight < 0) logFont.lfHeight = -logFont.lfHeight;

   rc.top = rc.bottom / logFont.lfHeight;
   int nPos = GetScrollPos(SB_VERT);
   if(nPos > 0)
   {
    nPos -= rc.top;
    if(nPos < 0) nPos = 0;
    SetScrollPos(SB_VERT,nPos);
    Invalidate();
   }
  }
  break;
// case SB_THUMBPOSITION://Scroll to the absolute position. The current position is provided in nPos.
case SB_THUMBTRACK://Drag scroll box to specified position. The current position is provided in nPos.
  {
   SetScrollPos(SB_VERT,nPos);
   Invalidate();
  }
  break;
// case SB_TOP://Scroll to top   
}

CWnd::OnVScroll(nSBCode, nPos, pScrollBar);
}

void CACComboBox::HandleCompletion()
{
// Make sure we can 'talk' to the edit control
if( m_pEdit == NULL )   
{
  m_pEdit = new CEdit();
  m_pEdit->SubclassWindow(GetDlgItem(1001)->GetSafeHwnd());
}

// Save the state of the edit control
CString text,bestText;
CInfoForACComboBox info;
int n = GetCount();

m_wndList.RemoveAll();
m_pEdit->GetWindowText(text);
CPoint ptCaret = m_pEdit->GetCaretPos();

// int start,end;
// m_pEdit->GetSel(start,end);

// Perform actual completion
int bestindex = -1;
int bestfrom  = INT_MAX;
int from;
for ( int x = 0; x < n; x++ )
{
  GetLBText(x,info.strDepict);
  info.nid = x;

  from = info.strDepict.Find(text);

  if(from != -1)
  {
   m_wndList.Add(info);
   if( from != -1 && from < bestfrom )
   {
    bestindex = x;
    bestText = info.strDepict;
    bestfrom = from;
   }
  }
}

if ( bestindex != -1)
{
  // Restore the edit control
  m_pEdit->SetWindowText(bestText);
  m_pEdit->SetSel(text.GetLength(),bestText.GetLength());
  m_pEdit->SetCaretPos(ptCaret);
}
if(m_wndList.GetSize() != 0)
{
  m_wndList.ShowList();
  m_wndList.Invalidate();
}
else
{
  m_wndList.ShowWindow(SW_HIDE);
}
}

BOOL CACComboBox::OnCommand(WPARAM wParam, LPARAM lParam)
{
if(HIWORD(wParam) == EN_CHANGE)
{
  HandleCompletion();
  return TRUE;
}
   
return CComboBox::OnCommand(wParam, lParam);
}

void CACComboBox::PreSubclassWindow()
{
CComboBox::PreSubclassWindow();

m_wndList.Create(this);
}

void CACComboBox::OnKillfocus()
{
m_wndList.OnKillFocus(GetFocus());
}

void CACComboBox::OnSelchange()
{
m_wndList.ShowWindow(SW_HIDE);
}