Dlg.h

private:
    adoConn *m_pAdoConn;
    int m_checked;
public:
    void updateCombo();
    void updateComboEnable();
    void renewListInfo();
    void clearListInfo();
    CString GetCollect(_RecordsetPtr pRset, CString str);

Dlg.cpp

CString Cschool3Dlg::GetCollect(_RecordsetPtr pRset, CString str)
{
    _variant_t var;
    CString strVal;
    var = pRset->GetCollect((_variant_t)str);
    if (var.vt != VT_NULL)
        strVal = (LPCSTR)_bstr_t(var);
    return strVal;
}

void Cschool3Dlg::updateCombo()
{
    CString vSQL = _T("select sname from student");
    _RecordsetPtr pRset = m_pAdoConn->ExcuteSQL(vSQL);
    CString str;
    while (!pRset->adoEOF)
    {
        str = GetCollect(pRset, _T("sname"));
        m_combo_sname.AddString(str);
        pRset->MoveNext();
    }

    vSQL = _T("select cname from course");
    pRset = m_pAdoConn->ExcuteSQL(vSQL);
    while (!pRset->adoEOF)
    {
        str = GetCollect(pRset, _T("cname"));
        m_combo_cname.AddString(str);
        pRset->MoveNext();
    }

}

void Cschool3Dlg::updateComboEnable()
{
    switch (m_checked)
    {
    case 0:
        m_combo_sname.EnableWindow(true);
        m_combo_cname.EnableWindow(false);
        break;
    case 1:
        m_combo_sname.EnableWindow(false);
        m_combo_cname.EnableWindow(true);
        break;
    default:
        break;
    }
}

void Cschool3Dlg::updateComboEnable()
{
    switch (m_checked)
    {
    case 0:
        m_combo_sname.EnableWindow(true);
        m_combo_cname.EnableWindow(false);
        break;
    case 1:
        m_combo_sname.EnableWindow(false);
        m_combo_cname.EnableWindow(true);
        break;
    default:
        break;
    }
}
void Cschool3Dlg::renewListInfo()
{
    clearListInfo();
    if (m_checked == 0)
    {
        m_listinfo.InsertColumn(0, _T("课程号"), 0, 60, -1);
        m_listinfo.InsertColumn(1, _T("课程名"), 0, 60, -1);
        CString str;
        CString vSQL;
        m_combo_sname.GetLBText(m_combo_sname.GetCurSel(), str);
        vSQL.Format(_T("select c.cno, c.cname from student as s join elective as e on s.sno = e.sno join course as c on  e.cno = c.cno where s.sname = '%s'"), str);
        _RecordsetPtr pRset = m_pAdoConn->ExcuteSQL(vSQL);
        int curItem = 0;
        while (!pRset->adoEOF)
        {
            str = GetCollect(pRset, _T("cno"));
            m_listinfo.InsertItem(curItem, str);

            str = GetCollect(pRset, _T("cname"));
            m_listinfo.SetItemText(curItem, 1, str);

            pRset->MoveNext();
            curItem++;
        }

    }
    else if (m_checked == 1)
    {
        m_listinfo.InsertColumn(0, _T("学生姓名"), 0, 60, -1);
        m_listinfo.InsertColumn(1, _T("分数"), 0, 60, -1);
        CString str;
        CString vSQL;
        m_combo_cname.GetLBText(m_combo_cname.GetCurSel(), str);
        vSQL.Format(_T("select s.sname, e.score from student as s join elective as e on s.sno = e.sno join course as c on  e.cno = c.cno where c.cname = '%s ' order by score desc"), str);
        _RecordsetPtr pRset = m_pAdoConn->ExcuteSQL(vSQL);
        int curItem = 0;
        while (!pRset->adoEOF)
        {
            str = GetCollect(pRset, _T("sname"));
            m_listinfo.InsertItem(curItem, str);

            str = GetCollect(pRset, _T("score"));
            m_listinfo.SetItemText(curItem, 1, str);

            pRset->MoveNext();
            curItem++;
        }

        m_combo_cname.GetLBText(m_combo_cname.GetCurSel(), str);
        vSQL.Format(_T("select avg(e.score) as avgscore from student as s join elective as e on s.sno = e.sno join course as c on  e.cno = c.cno where c.cname = '%s'"), str);
        pRset = m_pAdoConn->ExcuteSQL(vSQL);
        if (!pRset->adoEOF)
        {
            str = GetCollect(pRset, _T("avgscore"));
            m_static_avgscore.SetWindowTextW(str);
        }
    }
}

void Cschool3Dlg::clearListInfo()
{
    m_listinfo.DeleteAllItems();
    int n = m_listinfo.GetHeaderCtrl()->GetItemCount();
    for (int i = 0; i < n; i++)
        m_listinfo.DeleteColumn(0);
}

初始化内容

    CoInitialize(NULL);
    m_pAdoConn = new adoConn();
    m_checked = 0;
    m_radio_sname.SetCheck(true);
    updateComboEnable();

    updateCombo();
    m_combo_sname.SetCurSel(0);
    m_combo_cname.SetCurSel(0);