Count, propriété – Exemple (VC++)

S’applique à : Access 2013, Office 2013

Cet exemple illustre la propriété Count avec deux collections dans la base de données Employee . La propriété obtient le nombre d’objets de chaque collection et définit la limite supérieure pour les boucles qui énumèrent ces collections. Une autre façon d’énumérer ces collections sans utiliser la propriété Count consiste à utiliser des instructions.

 
// BeginCountCpp 
#import "C:\Program Files\Common Files\System\ADO\msado15.dll" no_namespace rename("EOF", "EndOfFile") 
 
#include <ole2.h> 
#include <stdio.h> 
#include<conio.h> 
 
// Function declarations 
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);}; 
void CountX(void); 
void PrintProviderError(_ConnectionPtr pConnection); 
void PrintComError(_com_error &e); 
 
/////////////////////////////////////////////////////////// 
// // 
// Main Function // 
// // 
/////////////////////////////////////////////////////////// 
 
void main() 
{ 
 if(FAILED(::CoInitialize(NULL))) 
 return; 
 
 CountX(); 
 
 //Wait here for user to see the output.. 
 printf("\nPress any key to Exit..."); 
 getch(); 
 
 ::CoUninitialize(); 
} 
 
/////////////////////////////////////////////////////////// 
// // 
// CountX Function // 
// // 
/////////////////////////////////////////////////////////// 
 
void CountX() 
{ 
 // Define ADO object pointers. 
 // Initialize pointers on define. 
 // These are in the ADODB:: namespace 
 _RecordsetPtr pRstEmployee = NULL; 
 
 //Define Other Variables 
 HRESULT hr = S_OK; 
 _variant_t Index; 
 Index.vt = VT_I2; 
 int j = 0; 
 
 _bstr_t strCnn("Provider='sqloledb';Data Source='MySqlServer';" 
 "Initial Catalog='pubs';Integrated Security='SSPI';"); 
 
 try 
 { 
 // Open recordset with data from Employee table. 
 TESTHR(pRstEmployee.CreateInstance(__uuidof(Recordset))); 
 pRstEmployee->Open("Employee", strCnn, adOpenForwardOnly, 
 adLockReadOnly, adCmdTable); 
 
 // Print information about Fields collection. 
 printf("%d Fields in Employee\n", pRstEmployee->Fields->Count); 
 for (int intLoop = 0; 
 intLoop <= (pRstEmployee->Fields->Count-1); 
 intLoop++) 
 { 
 Index.iVal = intLoop; 
 printf(" %s\n",(LPSTR) pRstEmployee->Fields-> 
 GetItem(Index)->Name); 
 } 
 
 // Print information about Properties collection. 
 printf("\n%d Properties in Employee\n", pRstEmployee-> 
 Properties->Count); 
 for (intLoop = 0; 
 intLoop <= (pRstEmployee->Properties->Count - 1); 
 intLoop++) 
 { 
 j++; 
 Index.iVal = intLoop; 
 printf(" %s\n" ,(LPSTR)pRstEmployee->Properties-> 
 GetItem(Index)->Name); 
 if (((j % 23) == 0) || (intLoop == 11)) 
 { 
 printf("\nPress any key to continue..."); 
 getch(); 
 
 //Clear the screen for the next display 
 system("cls"); 
 j = 0; 
 } 
 } 
 } 
 catch(_com_error &e) 
 { 
 // Notify user of any errors that result from 
 // executing the query. 
 // Pass a connection pointer accessed from the Recordset. 
 _variant_t vtConnect = pRstEmployee->GetActiveConnection(); 
 
 switch(vtConnect.vt) 
 { 
 case VT_BSTR: 
 PrintComError(e); 
 break; 
 case VT_DISPATCH: 
 PrintProviderError(vtConnect); 
 break; 
 default: 
 printf("Errors occured."); 
 break; 
 } 
 } 
 // Clean up objects before exit. 
 if (pRstEmployee) 
 if (pRstEmployee->State == adStateOpen) 
 pRstEmployee->Close(); 
} 
 
/////////////////////////////////////////////////////////// 
// // 
// PrintProviderError Function // 
// // 
/////////////////////////////////////////////////////////// 
 
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("Error number: %x\t%s\n",pErr->Number, 
 pErr->Description); 
 } 
 } 
} 
 
/////////////////////////////////////////////////////////// 
// // 
// PrintComError Function // 
// // 
/////////////////////////////////////////////////////////// 
 
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); 
} 
// EndCountCpp