Ejemplo de métodos MoveFirst, MoveLast, MoveNext y MovePrevious (VC++)

En este ejemplo se usa el MoveFirst, MoveLast, MoveNexty métodos movePrevious para mover el puntero de registro de un Recordset basado en el comando proporcionado. La función MoveAny es necesaria para que se ejecute este ejemplo.

Ejemplo

// MoveFirstMoveLastMoveNextSample.cpp  
// compile with: /EHsc  
#include <ole2.h>  
#include <stdio.h>  
  
#import "msado15.dll" no_namespace rename("EOF", "EndOfFile")  
  
// Function declarations  
inline void TESTHR(HRESULT x) { if FAILED(x) _com_issue_error(x); };  
void MoveFirstX();  
void MoveAny(int intChoice, _RecordsetPtr pRstTemp);  
void PrintProviderError(_ConnectionPtr pConnection);  
void PrintComError(_com_error &e);  
  
int main() {  
   if ( FAILED(::CoInitialize(NULL)) )  
      return -1;  
  
   MoveFirstX();  
   ::CoUninitialize();  
}  
  
void MoveFirstX() {  
   HRESULT hr = S_OK;  
   _RecordsetPtr pRstAuthors = NULL;  
   _bstr_t strCnn("Provider='sqloledb'; Data Source='My_Data_Source'; Initial Catalog='pubs'; Integrated Security='SSPI';");  
   _bstr_t strMessage("UPDATE Titles SET Type = "  
      "'psychology' WHERE Type = 'self_help'");  
   int intCommand = 0;  
  
   // Temporary string variable for type conversion for printing.  
   _bstr_t  bstrFName;  
   _bstr_t  bstrLName;  
  
   try {  
      // Open recordset from Authors table.  
      TESTHR(pRstAuthors.CreateInstance(__uuidof(Recordset)));  
      pRstAuthors->CursorType = adOpenStatic;  
  
      // Use client cursor to enable AbsolutePosition property.  
      pRstAuthors->CursorLocation = adUseClient;  
      pRstAuthors->Open("Authors", strCnn, adOpenStatic, adLockBatchOptimistic, adCmdTable);  
  
      // Show current record information and get user's method choice.  
      while (true) {   // Continuous loop.  
         // Convert variant string to convertible string type.  
         bstrFName = pRstAuthors->Fields->Item["au_fName"]->Value;  
         bstrLName = pRstAuthors->Fields->Item["au_lName"]->Value;  
  
         printf("Name: %s %s\n Record %d of %d\n\n",  
            (LPCSTR) bstrFName,  
            (LPCSTR) bstrLName,  
            pRstAuthors->AbsolutePosition,  
            pRstAuthors->RecordCount);  
         printf("[1 - MoveFirst, 2 - MoveLast, \n");  
         printf(" 3 - MoveNext, 4 - MovePrevious, 5 - Quit]\n");  
  
         scanf_s("%d", &intCommand);  
  
         if ((intCommand < 1) || (intCommand > 4))  
            break;   // Out of range entry exits program loop.  
  
         // Call method based on user's input.  
         MoveAny(intCommand, pRstAuthors);  
      }  
   }  
   catch (_com_error &e) {  
      // Notify the user of errors if any.  
      // Pass a connection pointer accessed from the Recordset.  
      _variant_t vtConnect = pRstAuthors->GetActiveConnection();  
  
      // GetActiveConnection returns connect string if connection  
      // is not open, else returns Connection object.  
      switch(vtConnect.vt) {  
         case VT_BSTR:  
            PrintComError(e);  
            break;  
         case VT_DISPATCH:  
            PrintProviderError(vtConnect);  
            break;  
         default:  
            printf("Errors occurred.");  
            break;  
      }  
   }  
  
   // Clean up objects before exit.  
   if (pRstAuthors)  
      if (pRstAuthors->State == adStateOpen)  
         pRstAuthors->Close();  
}  
  
void MoveAny(int intChoice, _RecordsetPtr pRstTemp) {  
   // Use specified method, trapping for BOF and EOF  
   try {  
      switch(intChoice) {  
         case 1:  
            pRstTemp->MoveFirst();  
            break;  
         case 2:  
            pRstTemp->MoveLast();  
            break;  
         case 3:  
            pRstTemp->MoveNext();  
            if (pRstTemp->EndOfFile) {  
               printf("\nAlready at end of recordset!\n");  
               pRstTemp->MoveLast();  
            }    // End If  
            break;  
         case 4:  
            pRstTemp->MovePrevious();  
            if (pRstTemp->BOF) {  
               printf("\nAlready at beginning of recordset!\n");  
               pRstTemp->MoveFirst();  
            }  
            break;  
         default:  
            ;  
      }  
   }  
  
   catch(_com_error &e) {  
      // Notify the user of errors if any.  
      // Pass a connection pointer accessed from the Recordset.  
      _variant_t vtConnect = pRstTemp->GetActiveConnection();  
  
      // GetActiveConnection returns connect string if connection  
      // is not open, else returns Connection object.  
      switch(vtConnect.vt)  {  
         case VT_BSTR:  
            PrintComError(e);  
            break;  
         case VT_DISPATCH:  
            PrintProviderError(vtConnect);  
            break;  
         default:  
            printf("Errors occurred.");  
            break;  
      }  
   }  
}  
  
void PrintProviderError(_ConnectionPtr pConnection) {  
   // Print Provider Errors from Connection object.  
  
   // pErr is a record object in the Connection's Error collection.  
   ErrorPtr pErr = NULL;  
  
   if ( (pConnection->Errors->Count) > 0) {  
      long nCount = pConnection->Errors->Count;  
      // Collection ranges from 0 to nCount - 1.  
      for ( long i = 0 ; i < nCount ; i++) {  
         pErr = pConnection->Errors->GetItem(i);  
         printf("\t Error number: %x\t%s", pErr->Number, pErr->Description);  
      }  
   }  
}  
  
void PrintComError(_com_error &e) {  
   _bstr_t bstrSource(e.Source());  
   _bstr_t bstrDescription(e.Description());  
  
   // Print Com errors.  
   printf("Error\n");  
   printf("\tCode = %08lx\n", e.Error());  
   printf("\tCode meaning = %s\n", e.ErrorMessage());  
   printf("\tSource = %s\n", (LPCSTR) bstrSource);  
   printf("\tDescription = %s\n", (LPCSTR) bstrDescription);  
}  

Entrada

5  

Consulte también

métodos MoveFirst, MoveLast, MoveNext y MovePrevious (ADO)
objeto Recordset (ADO)