📄 mdhowadotutorial(vc).htm

📁 ADO使用手册,非常详细
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<h3><a name="mdhowadotutorial(vc)"></a>ADO 教程 (VC++) </h3>
<p><a href="dir.htm">目录</a></p>
<p>
本教程以新版 Microsoft Visual C++ Extensions 为特征。VC++ Extensions 删除了对繁琐的 VARIANT 数据类型的使用。 </p>
<p>
本教程还使用了 <b>#import </b>伪指令，它将 ADO Typelib 转换到头文件中，这个头文件使一些 ADO 的功能在使用和外观上类似 Microsoft Visual Basic 中相应的用法。</p>
<p class=indent>
<B><b>注意</b></B>&nbsp;&nbsp;&nbsp;在该范例中发布和使用的绑定宏已经过更改，不再与原始文档相同。有关当前宏定义的详细信息，请参阅头文件 icrsint.h。</p>
<pre>#define INITGUID
#import "c:\Program Files\Common Files\System\ADO\msado15.dll" \
   no_namespace rename("EOF", "EndOfFile")
#include &lt;stdio.h&gt;
#include &lt;icrsint.h&gt;void dump_com_error(_com_error &amp;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,&nbsp;&nbsp;&nbsp;&nbsp;
         sizeof(m_szphone),&nbsp;&nbsp;&nbsp;&nbsp;lphoneStatus,&nbsp;&nbsp;&nbsp;&nbsp;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;// 步骤 1 — 打开连接      pConn-&gt;Open("dsn=pubs;", "sa", "", adConnectUnspecified);// 步骤 2 — 创建命令
// 步骤 3 — 执行命令      pRs-&gt;Open("select * from authors", 
         _variant_t(pConn),
         adOpenDynamic, adLockOptimistic, adCmdText);
      
      if (FAILED(hr = pRs-&gt;QueryInterface(__uuidof(IADORecordBinding), 
            (LPVOID*)&amp;picRs)))
         _com_issue_error(hr);
      
      if (FAILED(hr = picRs-&gt;BindToRecordset(&amp;rs)))
         _com_issue_error(hr);// 步骤 4 — 操作数据      pRs-&gt;Fields-&gt;GetItem("au_lname")-&gt;Properties-&gt;GetItem("Optimize")-&gt;Value = true; 
      pRs-&gt;Sort = "au_lname ASC";
      pRs-&gt;Filter = "phone LIKE '415 5*'";      pRs-&gt;MoveFirst();
      while (VARIANT_FALSE == pRs-&gt;EndOfFile)
         {
         printf("\a\tName: %s\t %s\tPhone: %s\n",&nbsp; 
            (rs.lau_fnameStatus == adFldOK ? rs.m_szau_fname : ""), 
            (rs.lau_lnameStatus == adFldOK ? rs.m_szau_lname : ""),
            (rs.lphoneStatus == adFldOK ? rs.m_szphone&nbsp;&nbsp; : ""));         if (rs.lphoneStatus == adFldOK)
            memcpy(rs.m_szphone, "777", 3);
            
         if (FAILED(hr = picRs-&gt;Update(&amp;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-&gt;MoveNext();
         }
      pRs-&gt;Filter = (long) adFilterNone;// 步骤 5 — 更新数据      pConn-&gt;BeginTrans();
      try 
         {
         pRs-&gt;UpdateBatch(adAffectAll);         // 步骤 6-A — 结束更新 
         pConn-&gt;CommitTrans();
         }      catch (_com_error)
         {
         // 步骤 6-B&nbsp; — 结束更新
         pRs-&gt;Filter = (long) adFilterConflictingRecords;
         pRs-&gt;MoveFirst();
         while (VARIANT_FALSE == pRs-&gt;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-&gt;MoveNext();
            }
         pConn-&gt;RollbackTrans();
         }
      }   catch (_com_error &amp;e)
      {
      dump_com_error(e);
      }   CoUninitialize();
   }
</pre>
<p>
<b>VC++ 教程到此结束。 </b></p>
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