MDAC 2.5 SDK - ADO

MoveFirst, MoveLast, MoveNext, and MovePrevious Methods Example (VC++)

See Also

This example uses the MoveFirst, MoveLast, MoveNext, and MovePrevious methods to move the record pointer of a Recordset based on the supplied command. The MoveAny function is required for this example to run.

#include <ole2.h>
#include <stdio.h>

#import "c:\Program Files\Common Files\System\ADO\msado15.dll" \
    no_namespace rename("EOF", "EndOfFile")

// Function declarations
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);};
void MoveFirstX();
void MoveAny(int intChoice, _RecordsetPtr pRstTemp);
void PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);

/////////////////////////////////
//      Main Function          //
/////////////////////////////////

void main()
{
    if(FAILED(::CoInitialize(NULL)))
        return;

    MoveFirstX();

    ::CoUninitialize();
}

//////////////////////////////////////
//      MoveFirstX Function         //
//////////////////////////////////////

void MoveFirstX() 
{
    HRESULT    hr = S_OK;
    _RecordsetPtr    pRstAuthors  = NULL;
    _bstr_t     strCnn("Provider=sqloledb;Data Source=srv;"
            "Initial Catalog=Pubs;User Id=sa;Password=;");
    _bstr_t strMessage("UPDATE Titles SET Type = "
            "'psychology' WHERE Type = 'self_help'");
    int intCommand = 0;

    // Temporary string variable for type conversion for printing.
    _bstr_t  bstrFName;
    _bstr_t  bstrLName;

    try
    {
        // Open recordset from Authors table.
        TESTHR(pRstAuthors.CreateInstance(__uuidof(Recordset)));
        pRstAuthors->CursorType = adOpenStatic;

        // Use client cursor to enable AbsolutePosition property.
        pRstAuthors->CursorLocation = adUseClient;
        pRstAuthors->Open("Authors", strCnn, adOpenStatic, 
            adLockBatchOptimistic, adCmdTable);

        // Show current record information and get user's method choice.
        while (true)  // Continuous loop.
        {
            // Convert variant string to convertable string type.
            bstrFName = pRstAuthors->Fields->Item["au_fName"]->Value;
            bstrLName = pRstAuthors->Fields->Item["au_lName"]->Value;

            printf("Name: %s %s\n Record %d of %d\n\n",
                (LPCSTR) bstrFName,
                (LPCSTR) bstrLName,
                pRstAuthors->AbsolutePosition,
                pRstAuthors->RecordCount);
            printf("[1 - MoveFirst, 2 - MoveLast, \n");
            printf(" 3 - MoveNext, 4 – MovePrevious, 5 - Quit]\n");

            scanf("%d", &intCommand);

            if ((intCommand < 1) || (intCommand > 4))
                break;   // Out of range entry exits program loop.

            // Call method based on user's input.
            MoveAny(intCommand, pRstAuthors);
        }

        pRstAuthors->Close();
    }
    catch (_com_error &e)
    {
       // Notify the user of errors if any.
       // Pass a connection pointer accessed from the Recordset.
        _variant_t vtConnect = pRstAuthors->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;
        }
    }
}

/////////////////////////////////
//      MoveAny Function       //
/////////////////////////////////

void MoveAny(int intChoice, _RecordsetPtr pRstTemp) 
{
    // Use specified method, trapping for BOF and EOF
    try
    {
        switch(intChoice)
        {
            case 1:
                pRstTemp->MoveFirst();
                break;
            case 2:
                pRstTemp->MoveLast();
                break;
            case 3:
                pRstTemp->MoveNext();
                if (pRstTemp->EndOfFile)
                {
                    printf("\nAlready at end of recordset!\n");
                    pRstTemp->MoveLast();
                }    //End If
                break;
            case 4:
                pRstTemp->MovePrevious();
                if (pRstTemp->BOF)
                {
                    printf("\nAlready at beginning of recordset!\n");
                    pRstTemp->MoveFirst();
                }
                break;
            default:
                ;
        }
    }

    catch(_com_error &e)
    {
       // Notify the user of errors if any.
       // Pass a connection pointer accessed from the Recordset.
        _variant_t vtConnect = pRstTemp->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,
                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);
}