Count-Eigenschaft (Beispiel) (VC++)

Gilt für: Access 2013, Office 2013

In diesem Beispiel wird die Count-Eigenschaft mit zwei Auflistungen in der Employee-Datenbank veranschaulicht. Die -Eigenschaft ruft die Anzahl der Objekte in jeder Auflistung ab und legt die Obergrenze für Schleifen fest, die diese Auflistungen aufzählen. Eine andere Möglichkeit, diese Auflistungen aufzulisten, ohne die Count-Eigenschaft zu verwenden, wäre die Verwendung von -Anweisungen.

 
// 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