Contoh Properti StayInSync (VC++)

Contoh ini menunjukkan bagaimana properti StayInSync memfasilitasi akses baris dalam Recordset hierarkis.

Perulangan luar menampilkan nama depan dan belakang, status, dan identifikasi setiap penulis. Recordset yang ditambahkan untuk setiap baris diambil dari koleksi Bidang dan secara otomatis ditetapkan ke rstTitleAuthor oleh properti StayInSync setiap kali Recordset induk berpindah ke baris baru. Perulangan dalam menampilkan empat bidang dari setiap baris dalam recordset yang ditambahkan.

// BeginStayInSyncCpp.cpp  
// compile with: /EHsc  
#import "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 StayInSyncX();  
void PrintProviderError(_ConnectionPtr pConnection);  
void PrintComError(_com_error &e);  
  
int main() {  
   if ( FAILED(::CoInitialize(NULL)) )  
      return -1 ;  
  
   StayInSyncX();  
   ::CoUninitialize();  
}  
  
void StayInSyncX() {  
   HRESULT  hr = S_OK;  
  
   // Define string variables.  
   _bstr_t strCnn("Provider='MSDataShape'; Data Provider='sqloledb'; Data Source='My_Data_Source'; Initial Catalog='pubs'; Integrated Security='SSPI';");  
  
   // Define ADO object pointers.  Initialize pointers on define.  
   // These are in the ADODB::  namespace.  
   _ConnectionPtr pConnection = NULL;  
   _RecordsetPtr pRst = NULL;  
   _RecordsetPtr pRstTitleAuthor = NULL;  
  
   try {  
      TESTHR(pRstTitleAuthor.CreateInstance(__uuidof(Recordset)));  
      TESTHR(pConnection.CreateInstance(__uuidof(Connection)));  
      TESTHR(pRst.CreateInstance(__uuidof(Recordset)));  
  
      // Open connection.  
      pConnection->Open (strCnn, "", "", adConnectUnspecified);  
      pRst->PutStayInSync(true);  
  
      // Open recordset with names from Author & titleauthor table.  
      pRst->Open("SHAPE  {select * from authors} "   
         "APPEND ({select * from titleauthor}"  
         "RELATE au_id TO au_id) AS chapTitleAuthor",  
         _variant_t((IDispatch*)pConnection, true), adOpenStatic, adLockReadOnly, adCmdText);  
  
      pRstTitleAuthor = pRst->GetFields()->GetItem("chapTitleAuthor")->Value;  
      while (!(pRst->EndOfFile)) {      
         printf("\n%s  %s  %s    %s\n", (LPCSTR)(_bstr_t)pRst->  
            Fields->GetItem("au_fname")->Value,  
            (LPCSTR)(_bstr_t)pRst->Fields->GetItem("au_lname")->Value,  
            (LPCSTR)(_bstr_t)pRst->Fields->GetItem("state")->Value,   
            (LPCSTR)(_bstr_t)pRst->Fields->GetItem("au_id")->Value);  
  
         _variant_t vIndex;  
         while ( !(pRstTitleAuthor->EndOfFile) ) {  
            vIndex = (short) 0;  
            printf("%s    ",(LPCSTR)(_bstr_t)pRstTitleAuthor->Fields->Item[&vIndex]->Value);  
            vIndex = (short) 1;  
            printf("%s    ",(LPCSTR)(_bstr_t)pRstTitleAuthor->Fields->Item[&vIndex]->Value);  
            vIndex = (short) 2;  
            printf("%s    ",(LPCSTR)(_bstr_t)pRstTitleAuthor->Fields->Item[&vIndex]->Value);  
            vIndex = (short) 3;  
            printf("%s\n",(LPCSTR)(_bstr_t)pRstTitleAuthor->Fields->Item[&vIndex]->Value);  
  
            pRstTitleAuthor->MoveNext();  
         }  
         pRst->MoveNext();  
      }  
   }  
   catch(_com_error &e) {  
      // Notify user of errors, if any.  Pass connection pointer accessed from the Recordset.  
      PrintProviderError(pConnection);  
      PrintComError(e);     
   }  
  
   // Clean up objects before exit.  
   if (pRst)  
      if (pRst->State == adStateOpen)  
         pRst->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;  
  
   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, (LPCSTR) 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);  
}  

Lihat juga

Koleksi Bidang (ADO)
Objek Recordset (ADO)
Properti StayInSync