Bof, eof, and bookmark properties example (VC ++)

MDAC 2.5 SDK-ado

 
Bof, eof, and bookmark properties example (VC ++)

The first function in this example uses the BOF and EOF properties to display a message if a user tries to move past the first or last record of A recordset. it uses the bookmark property to let the user flag a record inRecordsetAnd return to it later.

The second function uses the bookmark property to placeBookmarkOf every other record fromRecordsetInto an array, and then filters the recordset using the array.

#import "C:/Program Files/Common Files/System/ADO/msado15.dll" /    no_namespace rename("EOF", "EndOfFile")#include <ole2.h>#include <stdio.h>#include <conio.h>#include "BofEofBookmark.h"// Function declarationsinline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);};void BOFX(void);void BookmarkX(void);void PrintProviderError(_ConnectionPtr pConnection);void PrintComError(_com_error &e);/////////////////////////////////////////////////////////////                                                       ////      BOFX Function                                    ////                                                       /////////////////////////////////////////////////////////////void main(){    if(FAILED(::CoInitialize(NULL)))         return;    BOFX();    //Clear the screen for the next display       system("cls");     BookmarkX();    printf("Press any key to continue...");    getch();    ::CoUninitialize();}/////////////////////////////////////////////////////////////                                                       ////      BOFX Function                                    ////                                                       /////////////////////////////////////////////////////////////void BOFX(void) {    // Define ADO object pointers.    // Initialize pointers on define.    // These are in the ADODB::  namespace    _RecordsetPtr rstPublishers = NULL;    //Define Other Variables    HRESULT hr = S_OK;    IADORecordBinding  *picRs = NULL;    //Interface Pointer declared.    CPublishers Publs;    bstr_t strCnn("Provider=sqloledb;Data Source=srv;"        "Initial Catalog=Pubs;User Id=sa;Password=;");    _bstr_t strMessage;    _variant_t VarBookmark;    int intCommand = 0;    _variant_t TempPublisher;    try    {        // Open recordset with data from Publishers table.        TESTHR(rstPublishers.CreateInstance(__uuidof(Recordset)));          rstPublishers->CursorType = adOpenStatic;        // Use client cursor to enable AbsolutePosition property.        rstPublishers->CursorLocation = adUseClient;        rstPublishers->Open("select pub_id, pub_name from publishers"            " order by pub_name", strCnn, adOpenStatic,             adLockBatchOptimistic, adCmdText);        //Open an IADORecordBinding interface pointer         //which will be used for Binding Recordset to a class        TESTHR(rstPublishers->QueryInterface(            __uuidof(IADORecordBinding), (LPVOID*)&picRs));        //Bind the Recordset to a C++ Class here        TESTHR(picRs->BindToRecordset(&Publs));        rstPublishers->MoveFirst();         while (true)    // Continuous loop.        {            // Display information about the current record            // and get user input            printf("Publisher:%s /n Record %d of %d/n/n",                Publs.lP_pubnameStatus  == adFldOK ?                 Publs.m_szP_pubname : "<NULL>",                rstPublishers->AbsolutePosition,                 rstPublishers->RecordCount);            printf("Enter command:/n ");            printf("[1 - next          /  2 - previous       //n");            printf(" 3 - set bookmark  /  4 - go to bookmark //n");            printf(" 5 - quit                                ]/n");            scanf("%d", &intCommand);            if ((intCommand < 1) || (intCommand > 4))                break;    // Out of range entry exits program loop.            switch(intCommand)             {                // Move forward or backward, trapping for BOF or EOF                case 1:                    rstPublishers->MoveNext();                    if (rstPublishers->EndOfFile)                    {                        printf("/nCannot move past the last record."                               " Try again.../n");                        rstPublishers->MoveLast();                    }                    break;                case 2:                    rstPublishers->MovePrevious();                    if (rstPublishers->BOF)                    {                        printf("/nCannot move before the first record."                               " Try again.../n");                        rstPublishers->MoveFirst();                    }                    break;                // store the bookmark of the current record.                case 3:                    VarBookmark = rstPublishers->Bookmark;                    // Go to the record indicated by the                     // stored bookmark                    break;                case 4:                    // Check for whether bookmark set for a record                    if (VarBookmark.vt == VT_EMPTY)                        printf("No Bookmark set!/n");                    else                         rstPublishers->Bookmark = VarBookmark;                    break;                default:                    break;            }        }        // Clean up objects before exit.        rstPublishers->Close();        //Release the IADORecordset Interface here           if (picRs)            picRs->Release();    }    catch (_com_error &e)    {        printf("Error in BOFx.../n");        // Notify the user of errors if any.        _variant_t vtConnect = rstPublishers->GetActiveConnection();        // GetActiveConnection returns connect string if connection        // is not open, else returns Connection object.        switch(vtConnect.vt)        {            case VT_BSTR:                printf("Error:/n");                printf("Code = %08lx/n", e.Error());                printf("Message = %s/n", e.ErrorMessage());                printf("Source = %s/n", (LPCSTR) e.Source());                printf("Description = %s/n", (LPCSTR) e.Description());                break;            case VT_DISPATCH:                PrintProviderError(vtConnect);                break;            default:                printf("Errors occured.");                break;        }        printf("Press any key to continue...");        getch();    }}/////////////////////////////////////////////////////////////                                                       ////      BookmarkX Function                               ////                                                       /////////////////////////////////////////////////////////////void BookmarkX(void){    // Define ADO object pointers.    // Initialize pointers on define.    // These are in the ADODB::  namespace.    _RecordsetPtr rstAuthors = NULL;    //Define Other Variables    IADORecordBinding *picRs = NULL; //Interface Pointer declared.    CAuthors Authrs;    HRESULT  hr = S_OK;    _bstr_t  strCnn("Provider=sqloledb;Data Source=srv;"              "Initial Catalog=Pubs;User Id=sa;Password=;");    _variant_t vBookmark;    // Variable declaration for safe arrays.    SAFEARRAY FAR* psa;     // define ARRAY/ VARIANT variant.    vBookmark.vt = VT_ARRAY|VT_VARIANT;     SAFEARRAYBOUND rgsabound[1];    rgsabound[0].lLbound = 0;         rgsabound[0].cElements = 11;    long ii = 0;    try    {        rstAuthors.CreateInstance(__uuidof(Recordset));          // Set The Cursor Location        rstAuthors->CursorLocation  = adUseClient;        rstAuthors->PutActiveConnection((_variant_t)strCnn);            // Open Authors table        TESTHR(rstAuthors->Open("select * from Authors",strCnn,             adOpenStatic,adLockBatchOptimistic,adCmdText));        //Open an IADORecordBinding interface pointer         //which we'll use for binding Recordset to a class           TESTHR(rstAuthors->QueryInterface(__uuidof(IADORecordBinding),                 (LPVOID*)&picRs));        //Bind the Recordset to a C++ Class here         TESTHR(picRs->BindToRecordset(&Authrs));        printf("Number of Records before filtering:  %d/n",                 rstAuthors->RecordCount);        // Create safearrays to store array of variant         psa = SafeArrayCreate(VT_VARIANT,1,rgsabound);        // Store bookmark of every other record into an array.        while ((!rstAuthors->EndOfFile) && (ii < 11))        {            SafeArrayPutElement(psa,&ii,&rstAuthors->Bookmark);            //ii = ii +1;            ii++;            rstAuthors->Move(2);        }        vBookmark.parray = psa;        // Filter the Record with the array of bookmarks.        rstAuthors->put_Filter(vBookmark);        printf("Number of Records after filtering:  %d/n",             rstAuthors->RecordCount);        rstAuthors->MoveFirst();        while (!rstAuthors->EndOfFile)        {            printf("%d    %s/n",rstAuthors->AbsolutePosition,                 Authrs.lau_lnameStatus == adFldOK ?                 Authrs.m_szau_lname : "<NULL>");            rstAuthors->MoveNext();        }        //Release the IADORecordset Interface.        if (picRs)            picRs->Release();        // Clean up objects before exit.            rstAuthors->Close();    }    catch (_com_error &e)    {        // Notify the user of errors if any.        _variant_t vtConnect = rstAuthors->GetActiveConnection();        // GetActiveConnection returns connect string if connection        // is not open, else returns Connection object.        switch(vtConnect.vt)        {            case VT_BSTR:                printf("Error:/n");                printf("Code    = %08lx/n", e.Error());                printf("Message = %s/n", e.ErrorMessage());                printf("Source  = %s/n", (LPCSTR) e.Source());                printf("Description = %s/n", (LPCSTR) e.Description());                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;    long      nCount  = 0;    long      i       = 0;    if( (pConnection->Errors->Count) > 0)    {        nCount = pConnection->Errors->Count;        // Collection ranges from 0 to nCount -1.        for(i = 0; i < nCount; i++)        {            pErr = pConnection->Errors->GetItem(i);            printf("Error number: %x/t%s/n", pErr->Number,                (LPCSTR) pErr->Description);        }    }}

Bofeofbookmark. h:

#include "icrsint.h"//This Class extracts only pubid,lastname and hire_dateclass CPublishers : public CADORecordBinding{BEGIN_ADO_BINDING(CPublishers)    //Column title is the 2nd field in the recordset    ADO_VARIABLE_LENGTH_ENTRY2(1, adVarChar, m_szP_pubid,         sizeof(m_szP_pubid), lP_pubidStatus, FALSE)    //Column type is the 3rd field in the recordset    ADO_VARIABLE_LENGTH_ENTRY2(2, adVarChar, m_szP_pubname,         sizeof(m_szP_pubname), lP_pubnameStatus, TRUE)END_ADO_BINDING()public:    CHAR    m_szP_pubid;    ULONG   lP_pubidStatus;    CHAR    m_szP_pubname[40];    ULONG   lP_pubnameStatus;};//This Class extracts only authorlastnameclass CAuthors : public CADORecordBinding{BEGIN_ADO_BINDING(CAuthors)    //Column authorlname is the 2nd field in the recordset    ADO_VARIABLE_LENGTH_ENTRY2(2, adVarChar,  m_szau_lname,          sizeof(m_szau_lname), lau_lnameStatus, FALSE)END_ADO_BINDING()public:    CHAR    m_szau_lname[40];    ULONG   lau_lnameStatus;};