本教程以新版 Microsoft Visual C++ Extensions 為特征。VC++ Extensions 刪除了對繁瑣的 VARIANT 數(shù)據(jù)類型的使用。
本教程還使用了 #import 偽指令,它將 ADO Typelib 轉(zhuǎn)換到頭文件中,這個(gè)頭文件使一些 ADO 的功能在使用和外觀上類似 Microsoft Visual Basic 中相應(yīng)的用法。
注意 在該范例中發(fā)布和使用的綁定宏已經(jīng)過更改,不再與原始文檔相同。有關(guān)當(dāng)前宏定義的詳細(xì)信息,請參閱頭文件 icrsint.h。
#define INITGUID
#import "c:\Program Files\Common Files\System\ADO\msado15.dll" \
no_namespace rename("EOF", "EndOfFile")
#include <stdio.h>
#include <icrsint.h>
void dump_com_error(_com_error &e)
{
printf("Error\n");
printf("\a\tCode = %08lx\n", e.Error());
printf("\a\tCode meaning = %s", e.ErrorMessage());
_bstr_t bstrSource(e.Source());
_bstr_t bstrDescription(e.Description());
printf("\a\tSource = %s\n", (LPCSTR) bstrSource);
printf("\a\tDescription = %s\n", (LPCSTR) bstrDescription);
}
class CCustomRs :
public CADORecordBinding
{
BEGIN_ADO_BINDING(CCustomRs)
ADO_VARIABLE_LENGTH_ENTRY2(1, adVarChar, m_szau_lname,
sizeof(m_szau_lname), lau_lnameStatus, false)
ADO_VARIABLE_LENGTH_ENTRY2(2, adVarChar, m_szau_fname,
sizeof(m_szau_fname), lau_fnameStatus, false)
ADO_VARIABLE_LENGTH_ENTRY2(3, adVarChar, m_szphone,
sizeof(m_szphone), lphoneStatus, true)
END_ADO_BINDING()
public:
CHAR m_szau_lname[41];
ULONG lau_lnameStatus;
CHAR m_szau_fname[41];
ULONG lau_fnameStatus;
CHAR m_szphone[12];
ULONG lphoneStatus;
};
VOID main()
{
HRESULT hr;
IADORecordBinding *picRs = NULL;
::CoInitialize(NULL);
try
{
_ConnectionPtr pConn("ADODB.Connection.1.5");
_RecordsetPtr pRs("ADODB.Recordset.1.5");
CCustomRs rs;
// 步驟 1 — 打開連接
pConn->Open("dsn=pubs;", "sa", "", adConnectUnspecified);
// 步驟 2 — 創(chuàng)建命令
// 步驟 3 — 執(zhí)行命令
pRs->Open("select * from authors",
_variant_t(pConn),
adOpenDynamic, adLockOptimistic, adCmdText);
if (FAILED(hr = pRs->QueryInterface(__uuidof(IADORecordBinding),
(LPVOID*)&picRs)))
_com_issue_error(hr);
if (FAILED(hr = picRs->BindToRecordset(&rs)))
_com_issue_error(hr);
// 步驟 4 — 操作數(shù)據(jù)
pRs->Fields->GetItem("au_lname")->Properties->GetItem("Optimize")->Value = true;
pRs->Sort = "au_lname ASC";
pRs->Filter = "phone LIKE '415 5*'";
pRs->MoveFirst();
while (VARIANT_FALSE == pRs->EndOfFile)
{
printf("\a\tName: %s\t %s\tPhone: %s\n",
(rs.lau_fnameStatus == adFldOK ? rs.m_szau_fname : ""),
(rs.lau_lnameStatus == adFldOK ? rs.m_szau_lname : ""),
(rs.lphoneStatus == adFldOK ? rs.m_szphone : ""));
if (rs.lphoneStatus == adFldOK)
memcpy(rs.m_szphone, "777", 3);
if (FAILED(hr = picRs->Update(&rs)))
_com_issue_error(hr);
// Change the current row of the Recordset.
// Recordset data for the new current row will automatically be
// extracted and placed in the CCustomRs C++ instance variables.
pRs->MoveNext();
}
pRs->Filter = (long) adFilterNone;
// 步驟 5 — 更新數(shù)據(jù)
pConn->BeginTrans();
try
{
pRs->UpdateBatch(adAffectAll);
// 步驟 6-A — 結(jié)束更新
pConn->CommitTrans();
}
catch (_com_error)
{
// 步驟 6-B — 結(jié)束更新
pRs->Filter = (long) adFilterConflictingRecords;
pRs->MoveFirst();
while (VARIANT_FALSE == pRs->EndOfFile)
{
printf("\a\tConflict: Name = %s\t %s\n",
(rs.lau_fnameStatus == adFldOK ? rs.m_szau_fname : ""),
(rs.lau_lnameStatus == adFldOK ? rs.m_szau_lname : ""));
pRs->MoveNext();
}
pConn->RollbackTrans();
}
}
catch (_com_error &e)
{
dump_com_error(e);
}
CoUninitialize();
}
VC++ 教程到此結(jié)束。