Exemple de propriétés BOF, EOF et Bookmark (VC++)

La première fonction de cet exemple utilise les propriétés BOF et EOF pour afficher un message si un utilisateur tente de passer le premier ou le dernier enregistrement d’un recordset. Il utilise la propriété Bookmark pour permettre à l’utilisateur de marquer un enregistrement dans un recordset et de le retourner ultérieurement.

La deuxième fonction utilise la propriété Bookmark pour placer le signet de chaque autre enregistrement d’un Recordset dans un tableau, puis filtre l’objet Recordset à l’aide du tableau.

Exemple

// BOF_EOF_Bookmark.cpp  
// compile with: /EHsc  
#import "msado15.dll" no_namespace rename("EOF", "EndOfFile")  
  
#include <ole2.h>  
#include <stdio.h>  
#include "conio.h"  
#include "icrsint.h"  
  
// class extracts only author id,fname,lastname  
class CEmployeeRs : public CADORecordBinding {  
   BEGIN_ADO_BINDING(CEmployeeRs)  
  
   // Column au_id is the 1st field in the recordset     
   ADO_VARIABLE_LENGTH_ENTRY2(1, adVarChar, m_szau_id, sizeof(m_szau_id), lau_idStatus, TRUE)  
  
    ADO_VARIABLE_LENGTH_ENTRY2(2, adVarChar, m_szau_lname, sizeof(m_szau_lname), lau_lnameStatus, TRUE)  
  
    ADO_VARIABLE_LENGTH_ENTRY2(3, adVarChar, m_szau_fname, sizeof(m_szau_fname), lau_fnameStatus, TRUE)  
  
END_ADO_BINDING()  
  
public:  
   CHAR m_szau_id[20];  
   ULONG lau_idStatus;  
   CHAR m_szau_fname[40];  
   ULONG lau_fnameStatus;  
   CHAR   m_szau_lname[40];  
   ULONG  lau_lnameStatus;  
};  
  
// Function declaration  
inline void TESTHR(HRESULT x) { if FAILED(x) _com_issue_error(x); };  
void AppendX();  
void PrintProviderError(_ConnectionPtr pConnection);  
  
int main() {  
   HRESULT hr = S_OK;  
  
   if (FAILED(::CoInitialize(NULL)))  
        return -1;  
  
    AppendX();  
    ::CoUninitialize();   
}  
  
void AppendX() {  
   HRESULT hr = S_OK;  
  
   // Define ADO object pointers. Initialize pointers on define. These are in the ADODB::  namespace.  
   _RecordsetPtr pRstByRoyalty = NULL;  
   _RecordsetPtr pRstAuthors = NULL;    
   _CommandPtr pcmdByRoyalty = NULL;  
   _ParameterPtr pprmByRoyalty = NULL;  
   _ConnectionPtr pConnection = NULL;  
  
   //Define Other variables  
   IADORecordBinding *picRs = NULL;   // Interface Pointer declared.(VC++ Extensions)     
   CEmployeeRs emprs;   // C++ class object      
  
   _bstr_t strCnn("Provider='sqloledb'; Data Source='My_Data_Source'; Initial Catalog='pubs'; Integrated Security='SSPI';");  
  
   _bstr_t strMessage, strAuthorID;  
  
   int intRoyalty;  
   VARIANT vtRoyalty;  
  
   try {  
      // Open a Connection.  
      TESTHR(pConnection.CreateInstance(__uuidof(Connection)));  
      hr = pConnection->Open(strCnn, "", "", adConnectUnspecified);  
      pConnection->CursorLocation = adUseClient;  
  
      // Open Command Object with one Parameter  
      TESTHR(pcmdByRoyalty.CreateInstance(__uuidof(Command)));  
      pcmdByRoyalty->CommandText = "byroyalty";  
      pcmdByRoyalty->CommandType = adCmdStoredProc;  
  
      // Get parameter value and append parameter  
      printf("Enter Royalty: ");  
      scanf_s("%d", &intRoyalty);  
  
      // Define Integer/variant.  
      vtRoyalty.vt = VT_I2;  
      vtRoyalty.iVal = intRoyalty;  
      pprmByRoyalty = pcmdByRoyalty->CreateParameter("percentage", adInteger, adParamInput, sizeof(int), vtRoyalty);  
      pcmdByRoyalty->Parameters->Append(pprmByRoyalty);  
  
      pprmByRoyalty->Value = vtRoyalty;  
  
      // Create Recordset by executing the command  
      pcmdByRoyalty->ActiveConnection = pConnection;  
      pRstByRoyalty = pcmdByRoyalty->Execute(NULL, NULL, adCmdStoredProc);  
  
      // Open the authors table to get author names for display  
      TESTHR(pRstAuthors.CreateInstance(__uuidof(Recordset)));  
  
      // You have to explicitly pass the default Cursor type and LockType to the Recordset here  
      hr = pRstAuthors->Open("authors", _variant_t((IDispatch*)pConnection, true), adOpenForwardOnly, adLockReadOnly, adCmdTable);   
  
      // Open an IADORecordBinding interface pointer which we'll use for Binding Recordset to a class      
      TESTHR(pRstAuthors->QueryInterface(__uuidof(IADORecordBinding), (LPVOID*)&picRs));  
  
      // Bind the Recordset to a C++ Class here      
      TESTHR(picRs->BindToRecordset(&emprs));  
  
      // Print current data in the recordset, adding author names from author table.  
      printf("Authors with %d percent royalty ", intRoyalty);  
  
      while(!(pRstByRoyalty->EndOfFile)) {  
         strAuthorID = pRstByRoyalty->Fields->Item["au_id"]->Value;  
         pRstAuthors->Filter = "au_id = '"+strAuthorID+"'";  
  
         printf("\n"  "%s, %s  %s",emprs.lau_idStatus == adFldOK ? emprs.m_szau_id : "<NULL>",\  
            emprs.lau_fnameStatus == adFldOK ? emprs.m_szau_fname : "<NULL>",\  
            emprs.lau_lnameStatus == adFldOK ? emprs.m_szau_lname : "<NULL>");  
  
         pRstByRoyalty->MoveNext();   
      }  
   }  
   catch(_com_error &e) {  
      _bstr_t bstrSource(e.Source());  
      _bstr_t bstrDescription(e.Description());  
      PrintProviderError(pConnection);  
      printf("\n Source : %s \n Description : %s \n", (LPCSTR)bstrSource, (LPCSTR)bstrDescription);  
   }  
  
   // Clean up objects before exit.  Release the IADORecordset Interface here     
   if (picRs)  
      picRs->Release();  
  
   if (pRstByRoyalty)  
      if (pRstByRoyalty->State == adStateOpen)  
         pRstByRoyalty->Close();  
   if (pRstAuthors)  
      if (pRstAuthors->State == adStateOpen)  
         pRstAuthors->Close();  
   if (pConnection)  
      if (pConnection->State == adStateOpen)  
         pConnection->Close();  
}  
  
void PrintProviderError(_ConnectionPtr pConnection) {  
    // Print Provider Errors from Connection object.  
    // pErr is a record object in the Connection's Error collection.  
    ErrorPtr pErr = NULL;  
    long nCount = 0;  
    long i = 0;  
  
    if ( (pConnection->Errors->Count) > 0) {  
        nCount = pConnection->Errors->Count;  
        // Collection ranges from 0 to nCount -1.  
        for (i = 0 ; i < nCount ; i++) {  
            pErr = pConnection->Errors->GetItem(i);  
            printf("Error number: %x\n Error Description: %s\n", pErr->Number, (LPCSTR) pErr->Description);  
        }  
    }  
}  

Entrée

25  

Exemple de sortie

Authors with 25 percent royalty  
724-80-9391, Stearns  MacFeather  
899-46-2035, Anne  Ringer  

Voir aussi

BOF, EOF, propriétés (ADO)
Bookmark, propriété (ADO)
Recordset, objet (ADO)