C / C++ / MFC

LRESULT CUpdateDlg::OnThreadFinished(WPARAM wParam, LPARAM /*lParam*/)
{
  m_bSafeToClose = TRUE;
  EndDialog(IDCANCEL);
  return 0L;
}

CString CUpdateDlg::DownloadFile(const char *url, const char *filename)
{
  ... // remember to check for m_bTimeToDie

  PostMessage(WM_HTTPDOWNLOAD_THREAD_FINISHED);
  return (Cause);
}

void CUpdateDlg::OnCancel() 
{
    if(m_pThread){
      m_bTimeToDie=TRUE; // thread termination will 
      GetDlgItem(IDCANCEL)->EnableWindow(FALSE); // no more cancels, we already know
    }
    else EndDialog(IDCANCEL);
}

void CUpdateDlg::OnDestroy() 
{
  if(m_pThread){
    ::WaitForSingleObject(m_pThread->m_hThread,INFINITE);
    delete m_pThread;
    m_pThread=NULL;
  }

  CDialog::OnDestroy();
}

void CUpdateDlg::OnClose() 
{
  if(m_bSafeToClose)CDialog::OnClose();
  else{ //like OnCancel()
    if(m_pThread){
      m_bTimeToDie=TRUE;	
      GetDlgItem(IDCANCEL)->EnableWindow(FALSE);
    }
    else EndDialog(IDCANCEL);
  }
}