ADO Tutorial (VC++)

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This tutorial features the new Microsoft^® Visual C++^® Extensions. The VC++ Extensions eliminate the use of cumbersome VARIANT data types.

This tutorial also uses the #import directive, which converts the ADO typelib into a header file. That header file makes some ADO functionality similar in use and appearance to its equivalent in Microsoft^® Visual Basic^® .

#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_BINDING_ENTRY(1, adVarChar, m_szau_lname, 
         sizeof(m_szau_lname), lau_lnameStatus, FALSE)
   ADO_VARIABLE_LENGTH_BINDING_ENTRY(2, adVarChar, m_szau_fname, 
         sizeof(m_szau_fname), lau_fnameStatus, FALSE)
   ADO_FIXED_LENGTH_BINDING_ENTRY(3, adChar, 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;

// Step 1—Open a connection

      pConn->Open("dsn=pubs;uid=sa;pwd=;");

//Step 2—Create a command

// Step 3—Execute the command

      pRs->Open("select * from authors", pConn, 
         adOpenDynamic, adLockOptimistic, adCmdUnknown);
      
      if (FAILED(hr = pRs->QueryInterface(__uuidof(IADORecordBinding), 
            (LPVOID*)&picRs)))
         _com_issue_error(hr);
      
      if (FAILED(hr = picRs->BindToRecordset(&rs)))
         _com_issue_error(hr);

// Step 4—Manipulate the data

      pRs->Fields("au_lname").Optimize = TRUE;
      pRs->Sort = "au_lname ASCENDING";
      pRs->Filter = "phone LIKE '415 5*";

      pRs->MoveFirst();
      while (VARIANT_FALSE == pRs->EndOfFile)
         {
         printf("\a\tName: %s\t %s\tPhone: %s\n", 
            (lau_fnameStatus == adFldOK ? m_szau_fname : ""), 
            (lau_lnameStatus == adFldOK ? m_szau_lname): ""),
            (lau_lphoneStatus == adFldOK ? m_szphone): ""));

         if (lphoneStatus == adFldOK)
            lmemcpy(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 = adFilterNone;

// Step 5—Update the data

      pConn->BeginTrans();
      pRs->UpdateBatch();

// Step 6, part A—Conclude the update

      pConn->CommitTrans();
      }
   catch (_com_error &e)
      {
      dump_com_error(e);
      }
   catch (ADODB.Error &e)
      {
      pRS->Filter = adConflictingRecords;
      pRs->MoveFirst();
      while (VARIANT_FALSE == pRs->EndOfFile)
         {
         printf("\a\tConflict: Name = %s\t %s\n", 
            (lau_fnameStatus == adFldOK ? m_szau_fname : ""), 
            (lau_lnameStatus == adFldOK ? m_szau_lname): ""));
         pRs->MoveNext();
         }

// Step 6, part B—Conclude the update

      pConn->Rollback();
      }

   if (picRs)
      picRs->Release();

   CoUninitialize();
   }

This is the end of the VC++ tutorial.