Esempio del metodo Refresh (VC++)

In questo esempio viene illustrato l'uso del metodo Refresh per aggiornare la raccolta Parameters per un oggetto Command di una stored procedure.

Esempio

// BeginRefreshCpp.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"  
  
// Class extracts lname,fname from authors table.   
class CAuthorsRs : public CADORecordBinding {  
   BEGIN_ADO_BINDING(CAuthorsRs)  
  
   // Column lname is the 2nd field in the recordset  
   ADO_VARIABLE_LENGTH_ENTRY2(2, adVarChar, m_szau_lname,   
                              sizeof(m_szau_lname), lau_lnameStatus, TRUE)  
  
   // Column fname is the 3rd field in the recordset.  
   ADO_VARIABLE_LENGTH_ENTRY2(3, adVarChar, m_szau_fname,   
                              sizeof(m_szau_fname), lau_fnameStatus, TRUE)  
  
END_ADO_BINDING()  
  
public:  
   CHAR m_szau_fname[21];  
   ULONG lau_fnameStatus;      
   CHAR m_szau_lname[41];  
   ULONG lau_lnameStatus;  
};  
  
// Function declarations  
inline void TESTHR(HRESULT x) { if FAILED(x) _com_issue_error(x); };  
void RefreshX();  
void PrintProviderError(_ConnectionPtr pConnection);  
void PrintComError(_com_error &e);  
  
inline char* mygets(char* strDest, int n) {      
   char strExBuff[10];  
   char* pstrRet = fgets(strDest, n, stdin);  
  
   if (pstrRet == NULL)  
      return NULL;  
  
   if (!strrchr(strDest, '\n'))  
      // Exhaust the input buffer.  
      do {  
         fgets(strExBuff, sizeof(strExBuff), stdin);  
      } while (!strrchr(strExBuff, '\n'));  
   else  
      // Replace '\n' with '\0'  
      strDest[strrchr(strDest, '\n') - strDest] = '\0';  
  
   return pstrRet;  
}  
  
int main() {  
   if (FAILED(::CoInitialize(NULL)))  
      return -1;  
  
   RefreshX();  
   ::CoUninitialize();  
}  
  
void RefreshX() {  
   HRESULT  hr = S_OK;  
  
   // Define string variables.  
   _bstr_t strCnn("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;  
   _CommandPtr pCmdByRoyalty = NULL;  
   _RecordsetPtr pRstByRoyalty = NULL;  
   _RecordsetPtr pRstAuthors = NULL;  
   IADORecordBinding *picRs = NULL;   // Interface Pointer declared.   
   CAuthorsRs authorsrs;   // C++ class object  
   char * token1;  
  
   try {  
      // Open connection.  
      TESTHR(pConnection.CreateInstance(__uuidof(Connection)));  
      pConnection->Open (strCnn, "", "", adConnectUnspecified);  
  
      // Open a command object for a stored procedure, with one parameter.  
      TESTHR(pCmdByRoyalty.CreateInstance(__uuidof(Command)));  
      pCmdByRoyalty->ActiveConnection = pConnection;  
      pCmdByRoyalty->CommandText = "byroyalty";  
      pCmdByRoyalty->CommandType = adCmdStoredProc;  
      pCmdByRoyalty->Parameters->Refresh();  
  
      // Get parameter value and execute the command, storing the results in a recordset.  
      char *strRoyalty;  
      char strTemp[5];  
      do {  
         printf("\n\nEnter royalty : ");  
         mygets(strTemp, 5);  
  
         strRoyalty = strtok_s(strTemp," \t", &token1);  
         if (strRoyalty == NULL) {  
            exit(1);  
         }  
  
         // if the input is not numeric then notify the user.  
         if (!atoi(strRoyalty)) {  
            printf("\nExpecting numeric value...");  
            continue;  
         }  
      } while (!atoi(strRoyalty));  
  
      _variant_t vtroyal;  
      vtroyal.vt = VT_I2;  
      vtroyal.iVal = atoi(strRoyalty);  
      _variant_t Index;  
      Index.vt = VT_I2;  
      Index.iVal = 1;  
      pCmdByRoyalty->GetParameters()->GetItem(Index)->PutValue(vtroyal);  
      pRstByRoyalty = pCmdByRoyalty->Execute(NULL,NULL,adCmdStoredProc);  
  
      // Open the Authors table to get author names for display.  
      TESTHR(pRstAuthors.CreateInstance(__uuidof(Recordset)));  
      pRstAuthors->Open ("authors", _variant_t((IDispatch *) pConnection, true),  
         adOpenForwardOnly, adLockReadOnly, adCmdTable);  
  
      // Open an IADORecordBinding interface pointer which we'll use for   
      // Binding Recordset to a class.  
      TESTHR(pRstAuthors->QueryInterface(__uuidof(IADORecordBinding),(LPVOID*)&picRs));  
  
      // Bind the Recordset to a C++ Class here.  
      TESTHR(picRs->BindToRecordset(&authorsrs));  
  
      // Print current data in the recordset,adding   
      // author names from Authors table.  
      printf("Authors with %s percent royalty\n\n", strRoyalty);  
      while (!(pRstByRoyalty->EndOfFile)) {  
         _bstr_t strAuthorID = pRstByRoyalty->Fields->GetItem("au_id")->Value;  
  
         printf("  %s",(LPCSTR) (_bstr_t) pRstByRoyalty->Fields->GetItem("au_id")->Value);  
  
         pRstAuthors->Filter = "au_id ='"+strAuthorID+"'";  
         printf(", %s %s\n",authorsrs.lau_fnameStatus == adFldOK ?   
            authorsrs.m_szau_fname : "<NULL>",  
            authorsrs.lau_lnameStatus == adFldOK ?   
            authorsrs.m_szau_lname : "<NULL>");  
         pRstByRoyalty->MoveNext();  
      }  
   }  
   catch (_com_error &e) {  
      PrintProviderError(pConnection);  
      PrintComError(e);  
   }  
  
   if (pRstByRoyalty)  
      if (pRstByRoyalty->State == adStateOpen)  
         pRstByRoyalty->Close();  
   if (pRstAuthors)  
      if (pRstAuthors->State == adStateOpen)  
         pRstAuthors->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("\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);  
}  

Input di esempio

25  

Output di esempio

Authors with 25 percent royalty  
  
  724-80-9391, Stearns MacFeathe  
  899-46-2035, Anne Ringer  

Vedere anche

Oggetto Command (ADO)
Raccolta Parameters (ADO)
Metodo Refresh (ADO)