MarshalOptions Property Example (VC++)

This example uses the MarshalOptions property to specify what rows are sent back to the server — All Rows or only Modified Rows.

// BeginMarshalOptionsCpp.cpp  
// compile with: /EHsc /c  
#import "msado15.dll" no_namespace rename("EOF", "EndOfFile")  

#include <stdio.h>  
#include <ole2.h>  
#include <conio.h>  
#include <malloc.h>  
#include "icrsint.h"  

// This Class extracts only fname,lname from employees table  
class CEmployeeRs : public CADORecordBinding {  

   BEGIN_ADO_BINDING(CEmployeeRs)  

   // Column fname is the 1st field in the recordset  
   ADO_VARIABLE_LENGTH_ENTRY2(1, adVarChar, m_szemp_fname, sizeof(m_szemp_fname), lemp_fnameStatus, TRUE)  

   // Column lname is the 2nd field in the recordset  
   ADO_VARIABLE_LENGTH_ENTRY2(2, adVarChar, m_szemp_lname, sizeof(m_szemp_lname), lemp_lnameStatus, TRUE)  

   END_ADO_BINDING()  

public:  
   CHAR m_szemp_fname[21];  
   ULONG lemp_fnameStatus;  
   CHAR m_szemp_lname[31];  
   ULONG lemp_lnameStatus;  
};  

// Function declarations  
inline void TESTHR(HRESULT x) { if FAILED(x) _com_issue_error(x); };  
void MarshalOptionsX();  
void PrintProviderError(_ConnectionPtr pConnection);  
void PrintComError(_com_error &e);  

int main() {  
   if (FAILED(::CoInitialize(NULL)))  
      return -1;  

   MarshalOptionsX();  
   ::CoUninitialize();  
}  

void MarshalOptionsX() {  
   // Define string variables  
   char * token1;  
   _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.  
   _RecordsetPtr pRstEmployees = NULL;  

   // Define Other Variables  
   IADORecordBinding *picRs = NULL;   // Interface Pointer declared  
   CEmployeeRs emprs;   // C++ Class Object  
   HRESULT hr = S_OK;  
   LPSTR strOldFirst = NULL;  
   LPSTR strOldLast = NULL;  

   try {              
      // Open recordset with names from Employee table.  
      TESTHR(pRstEmployees.CreateInstance(__uuidof(Recordset)));  
      pRstEmployees->CursorType = adOpenKeyset;  
      pRstEmployees->LockType = adLockOptimistic;  
      pRstEmployees->CursorLocation = adUseClient;  
      pRstEmployees->Open("SELECT fname, lname FROM Employee ORDER BY lname", strCnn,   
                           adOpenKeyset, adLockOptimistic, adCmdText);  

      // Open an IADORecordBinding interface pointer which   
      // we'll use 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));  

      // Store Original Data  
      strOldFirst = (LPSTR) malloc(sizeof(emprs.m_szemp_fname));  
      strOldLast  = (LPSTR) malloc(sizeof(emprs.m_szemp_lname));  

      // Set the final character of the destination string to NULL.  
      strOldFirst[sizeof(emprs.m_szemp_fname)-1] = '\0';  

      // The source string will get truncated if its length is   
      // longer than the length of the destination string minus one.  
      strncpy_s(strOldFirst, sizeof(emprs.m_szemp_lname), strtok_s(emprs.m_szemp_fname, " ", &token1), sizeof(emprs.m_szemp_fname) - 1);  

      // Set the final character of the destination string to NULL.  
      strOldLast[sizeof(emprs.m_szemp_lname) - 1] = '\0';  

      // The source string will get truncated if its length is   
      // longer than the length of the destination string minus one.  
      strncpy_s(strOldLast, sizeof(emprs.m_szemp_lname), strtok_s(emprs.m_szemp_lname," ", &token1), sizeof(emprs.m_szemp_lname) - 1);  

      // Change Data in Edit Buffer.  Set the final character of the destination string to NULL.  
      emprs.m_szemp_fname[sizeof(emprs.m_szemp_fname) - 1] = '\0';  

      // The source string will be truncated if its length is longer than the length of the destination string minus one.  
      strncpy_s(emprs.m_szemp_fname, _countof(emprs.m_szemp_fname), "Linda", sizeof(emprs.m_szemp_fname) -1);  

      // Set the final character of the destination string to NULL.  
      emprs.m_szemp_lname[sizeof(emprs.m_szemp_lname)-1] = '\0';  

      // The source string will be truncated if its length is longer than the destination string minus one.  
      strncpy_s(emprs.m_szemp_lname, _countof(emprs.m_szemp_lname), "Kobara", sizeof(emprs.m_szemp_lname) -1);  

      // Show contents of buffer and get user input  
      printf("Edit in Progress:\n");  
      printf("Original Data = %s  %s \n",strOldFirst,strOldLast);  
      printf("Data in buffer = %s  %s \n", emprs.lemp_fnameStatus == adFldOK ? emprs.m_szemp_fname : "<NULL>",  
                                           emprs.lemp_lnameStatus == adFldOK ? emprs.m_szemp_lname : "<NULL>");  
      printf("Use Update to replace the original data with the buffered data in the Recordset?\nEnter (y/n) :?");  
      char opt1 = _getch();  

      if (toupper(opt1)=='Y') {  
         printf("\nWould you like to send all the rows in the recordset back to the server?\nEnter (y/n):");  
         char opt2 = _getch();  
         if (toupper(opt2) == 'Y') {  
            pRstEmployees->MarshalOptions = adMarshalAll;  
            picRs->Update(&emprs);  
         }  
      }  
      else {  
         printf("\nWould you like to send only modified rows back to the server?\nEnter (y/n):");  
         char opt3 = _getch();  
         if (toupper(opt3) == 'Y') {  
            pRstEmployees->MarshalOptions = adMarshalModifiedOnly;  
            picRs->Update(&emprs);  
         }  
      }  

      // Show the resulting data  
      printf("\nData In the Recordset = %s  %s\n",  
             emprs.lemp_fnameStatus == adFldOK ?   
             emprs.m_szemp_fname : "<NULL>",  
             emprs.lemp_lnameStatus == adFldOK ?   
             emprs.m_szemp_lname : "<NULL>");  

      // Restore original data because this is a demonstration    
      if ((strcmp(strOldFirst,emprs.m_szemp_fname)) && (strcmp(strOldLast, emprs.m_szemp_lname))) {  
         // Set the final character of the destination string to NULL.  
         emprs.m_szemp_fname[sizeof(emprs.m_szemp_fname)-1] = '\0';  

         // The source string will get truncated if its length is   
         // longer than the length of the destination string minus one.  
         strncpy_s(emprs.m_szemp_fname, _countof(emprs.m_szemp_fname), strOldFirst, sizeof(emprs.m_szemp_fname)-1);  

         // Set the final character of the destination string to NULL.  
         emprs.m_szemp_lname[sizeof(emprs.m_szemp_lname)-1] = '\0';  

         // The source string will get truncated if its length is   
         // longer than the length of the destination string minus one.  
         strncpy_s(emprs.m_szemp_lname, _countof(emprs.m_szemp_lname), strOldLast, sizeof(emprs.m_szemp_lname) -1);   
         picRs->Update(&emprs);  
      }  
   }  
   catch(_com_error &e) {  
      // Notify the user of errors if any.  
      // Pass a connection pointer accessed from the Recordset.  
      _variant_t vtConnect = pRstEmployees->GetActiveConnection();  

      // GetActiveConnection returns connect string if connection  
      // is not open, else returns Connection object.  
      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.  
   // Deallocate memory  
   if (strOldFirst)  
      free(strOldFirst);  
   if (strOldLast)  
      free(strOldLast);  

   // 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;  

   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, (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);  
}  

See Also

MarshalOptions Property (ADO)