Ejemplo de propiedades AbsolutePosition y CursorLocation (VC ++)

En este ejemplo se muestra cómo la propiedad AbsolutePosition puede realizar un seguimiento del progreso de un bucle que enumera todos los registros de un objeto Recordset. Se usa la propiedad CursorLocation para habilitar la propiedad AbsolutePosition estableciendo el cursor en un cursor de cliente.

// BeginAbsolutePositionCpp.cpp  
// compile with: /EHsc /c  
#import "msado15.dll" no_namespace rename("EOF", "EndOfFile")  
  
#include <ole2.h>  
#include <stdio.h>  
#include "conio.h"   
#include "icrsint.h"  
  
// This class extracts last name.    
class CEmployeeRs : public CADORecordBinding {  
   BEGIN_ADO_BINDING(CEmployeeRs)  
      // Column lname is the 4th field in the recordset     
      ADO_VARIABLE_LENGTH_ENTRY2(4, adVarChar, m_szau_lname,   
      sizeof(m_szau_lname), lau_lnameStatus, TRUE)  
   END_ADO_BINDING()  
  
public:  
   CHAR   m_szau_lname[41];  
   ULONG  lau_lnameStatus;  
  
};  
  
//Function Declarations  
inline void TESTHR(HRESULT x) { if FAILED(x) _com_issue_error(x); };  
  
void AbsolutePositionX();  
void AbsolutePosition2X();  
void PrintProviderError(_ConnectionPtr pConnection);  
  
int main() {  
   if ( FAILED(::CoInitialize(NULL)) )  
      return -1;  
  
   AbsolutePositionX();  
  
   // Clear the screen for the next display     
   printf("Press any key to continue...");  
   _getch();  
   system("cls");   
  
   AbsolutePosition2X();  
  
   ::CoUninitialize();  
}  
  
void AbsolutePositionX() {  
   HRESULT hr = S_OK;    
  
   // Define ADO object pointers.  // Initialize pointers on define.  
   // These are in the ADODB:: namespace.  
   _RecordsetPtr pRstEmployees = NULL;  
  
   // Define other variables.  Interface Pointer declared.(VC++ Extensions)  
   IADORecordBinding *picRs = NULL;  
   CEmployeeRs emprs;   // C++ class object  
   _bstr_t strMessage;  
   char chKey;  
  
   // Open a recordset using a client cursor for the Employee table.  
  
   _bstr_t strCnn("Provider='sqloledb'; Data Source='My_Data_Source'; Initial Catalog='pubs'; Integrated Security='SSPI';");  
  
   try {  
      // Open a recordset.  
      TESTHR(pRstEmployees.CreateInstance(__uuidof(Recordset)));  
  
      // Use client cursor to enable AbsolutePosition property.  
      pRstEmployees->CursorLocation = adUseClient;  
  
      // Explicitly pass the default Cursor type and LockType to the recordset.  
      TESTHR(pRstEmployees->Open("employee", strCnn, adOpenForwardOnly, adLockReadOnly, adCmdTable));  
  
      // Open an IADORecordBinding interface pointer for binding the recordset to a class.  
      TESTHR(pRstEmployees->QueryInterface(__uuidof(IADORecordBinding),(LPVOID*)&picRs));  
  
      // Bind the recordset to a C++ class here.     
      TESTHR(picRs->BindToRecordset(&emprs));  
  
      strMessage= "";  
  
      // Enumerate recordset  
      do {  
         // Display current record information.  
         printf("Employee : %s \n record %ld of %d",   
            emprs.lau_lnameStatus == adFldOK ?   
            emprs.m_szau_lname : "<NULL>",  
            pRstEmployees->AbsolutePosition,   
            pRstEmployees->RecordCount);  
  
         printf("\nContinue?(y/n)  :");  
  
         do {  
            chKey = _getch();  
         } while (chKey != 'y' && chKey !='n');  
  
         // Clear the Screen for the next output     
         system("cls");  
  
         if (chKey == 'n')  
            break;  
  
         strMessage = "";     
         pRstEmployees->MoveNext();     
      } while (!(pRstEmployees->EndOfFile));  
   }  
   catch(_com_error &e) {  
      // Notify the user of errors, if any.  
      _variant_t vtConnect = pRstEmployees->GetActiveConnection();  
  
      // GetActiveConnection returns connect string if connection  
      // is not open, else returns Connection object.  
      switch(vtConnect.vt) {  
      case VT_BSTR:  
         printf("Error:\n");  
         printf("Code = %08lx\n", e.Error());  
         printf("Message = %s\n", e.ErrorMessage());  
         printf("Source = %s\n", (LPCSTR) e.Source());  
         printf("Description = %s\n", (LPCSTR) e.Description());  
         break;  
      case VT_DISPATCH:  
         PrintProviderError(vtConnect);  
         break;  
      default:  
         printf("Errors occurred.");  
         break;  
      }  
   }  
  
   // Clean up objects before exit.  Release the IADORecordset Interface here.   
   if (picRs)  
      picRs->Release();  
  
   if (pRstEmployees)  
      if (pRstEmployees->State == adStateOpen)  
         pRstEmployees->Close();  
}  
  
void AbsolutePosition2X() {  
   HRESULT hr = S_OK;    
  
   // Define ADO object pointers.  Initialize pointers on define.  
   // These are in the ADODB:: namespace.  
   _RecordsetPtr pRstEmployees = NULL;  
  
   // Define Other Variables.  Interface Pointer declared.(VC++ Extensions)  
   IADORecordBinding *picRs = NULL;  
   CEmployeeRs emprs;   // C++ class object  
   _bstr_t strMessage;  
  
   // Open a recordset using a client cursor for the Employee table.  
   _bstr_t strCnn("Provider='sqloledb'; Data Source='My_Data_Source'; Initial Catalog='pubs'; Integrated Security='SSPI';");  
  
   try {  
      // Open a recordset.  
      TESTHR(pRstEmployees.CreateInstance(__uuidof(Recordset)));  
  
      // Use client cursor to enable Absoluteposition property.  
      pRstEmployees->CursorLocation = adUseClient;  
  
      // Explicitly pass the default Cursor type and LockType to the Recordset.  
      TESTHR(pRstEmployees->Open("employee", strCnn, adOpenStatic, adLockReadOnly, adCmdTable));  
  
      // Open an IADORecordBinding interface pointer for Binding Recordset to a class.  
      TESTHR(pRstEmployees->QueryInterface(__uuidof(IADORecordBinding),(LPVOID*)&picRs));  
  
      // Bind the Recordset to a C++ Class here.   
      TESTHR(picRs->BindToRecordset(&emprs));  
  
      long lGoToPos = 21;  
  
      pRstEmployees->AbsolutePosition = (PositionEnum)lGoToPos;  
  
      // Display current record information.  
      printf("Employee : %s \n record %ld of %d",   
         emprs.lau_lnameStatus == adFldOK ? emprs.m_szau_lname : "<NULL>", pRstEmployees->AbsolutePosition,   
         pRstEmployees->RecordCount);  
  
      printf("\nPress any key to continue:");  
      _getch();  
   }  
   catch(_com_error &e) {  
      // Notify the user of errors if any.  
      _variant_t vtConnect = pRstEmployees->GetActiveConnection();  
  
      // GetActiveConnection returns connect string if connection  
      // is not open, else returns Connection object.  
      switch(vtConnect.vt) {  
      case VT_BSTR:  
         printf("Error:\n");  
         printf("Code = %08lx\n", e.Error());  
         printf("Message = %s\n", e.ErrorMessage());  
         printf("Source = %s\n", (LPCSTR) e.Source());  
         printf("Description = %s\n", (LPCSTR) e.Description());  
         break;  
      case VT_DISPATCH:  
         PrintProviderError(vtConnect);  
         break;  
      default:  
         printf("Errors occurred.");  
         break;  
      }  
   }  
  
   // Clean up objects before exit. Release the IADORecordset Interface here.    
   if (picRs)  
      picRs->Release();  
  
   if (pRstEmployees)  
      if (pRstEmployees->State == adStateOpen)  
         pRstEmployees->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("\t Error number: %x\t%s", pErr->Number, (LPCSTR) pErr->Description);  
      }  
   }  
}  

Consulte también

Propiedad AbsolutePosition (ADO)
Propiedad CursorLocation (ADO)
Objeto de conjunto de registros (ADO)