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.
#import "C:\Program Files\Common Files\System\ADO\msado15.dll" \
no_namespace rename("EOF", "EndOfFile")
#include <stdio.h>
#include <ole2.h>
#include <conio.h>
#include <malloc.h>
#include "MarshalOptionsX.h"
// Function declarations
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);};
void MarshalOptionsX(void);
void PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);
///////////////////////////////////////////////////////////
// //
// Main Function //
// //
///////////////////////////////////////////////////////////
void main()
{
if(FAILED(::CoInitialize(NULL)))
return;
MarshalOptionsX();
::CoUninitialize();
}
///////////////////////////////////////////////////////////
// //
// Marshal Options Function //
// //
///////////////////////////////////////////////////////////
void MarshalOptionsX(void)
{
// Define string variables
_bstr_t strCnn("Provider=sqloledb;Data Source=srv;"
"Initial Catalog=Pubs;User Id=sa;Password=;");
// 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
CEmployeesRs emprs; //C++ Class Object
HRESULT hr = S_OK;
try
{
// Open recordset with names from Employees table.
TESTHR(pRstEmployees.CreateInstance(__uuidof(Recordset)));
pRstEmployees->CursorType = adOpenKeyset;
pRstEmployees->LockType = adLockOptimistic;
pRstEmployees->CursorLocation = adUseClient;
pRstEmployees->Open("SELECT fname, lname FROM Employees "
"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
LPSTR strOldFirst = (LPSTR) malloc(sizeof(emprs.m_szemp_fname));
LPSTR strOldLast = (LPSTR) malloc(sizeof(emprs.m_szemp_lname));
strcpy(strOldFirst,strtok(emprs.m_szemp_fname," "));
strcpy(strOldLast,strtok(emprs.m_szemp_lname," "));
//Change Data in Edit Buffer
strcpy(emprs.m_szemp_fname,"Linda");
strcpy(emprs.m_szemp_lname,"Kobara");
// 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)))
{
strcpy(emprs.m_szemp_fname,strOldFirst);
strcpy(emprs.m_szemp_lname,strOldLast);
picRs->Update(&emprs);
}
// Deallocate memory
free(strOldFirst);
free(strOldLast);
// Release IADORecordset Interface
if (picRs)
picRs->Release();
// Clean up objects before exit.
pRstEmployees->Close();
}
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;
}
}
}
///////////////////////////////////////////////////////////
// //
// 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("\t Error number: %x\t%s", pErr->Number,
(LPCSTR) 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);
}
MarshalOptionsX.h:
// MarshalOptionsX.h
#include "icrsint.h"
//This Class extracts only fname,lname from employees table
class CEmployeesRs : public CADORecordBinding
{
BEGIN_ADO_BINDING(CEmployeesRs)
//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;
};