MDAC 2.5 SDK - ADO

Supports Method Example (VC++)

See Also

This example uses the Supports method to display the options supported by a recordset opened with different cursor types. The DisplaySupport function is required for this example to run.

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

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

//Function Declarations.
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);};
void SupportsX(void);
void DisplaySupport(_RecordsetPtr pRstTemp);
void PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);

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

    SupportsX();

    ::CoUninitialize();
}

///////////////////////////////////////////////
//                                           //
//    SupportsX Function                     //
//                                           //
///////////////////////////////////////////////
void SupportsX(void)
{
    // Define ADO object pointers.
    // Initialize pointers on define.
    // These are in the ADODB::  namespace.
    _RecordsetPtr  pRstTitles  = NULL;

    // Define Other Variables
    HRESULT hr = S_OK;

    // Assign connection string to a variable
    _bstr_t strCnn("Provider=sqloledb;Data Source=srv;"
            "Initial Catalog=Pubs;User Id=sa;Password=;");

    try
    {
        // Open a recordset from Titles table
        TESTHR(pRstTitles.CreateInstance(__uuidof(Recordset)));

        // Fill array with CursorType constants.
        int  aintCursorType[4];
        aintCursorType[0] = adOpenForwardOnly;
        aintCursorType[1] = adOpenKeyset;
        aintCursorType[2] = adOpenDynamic;
        aintCursorType[3] = adOpenStatic;

        // Open recordset using each CursorType and optimistic locking.
        // Then call the DisplaySupport procedure to display the
        // supported options.
        for (int intIndex=0; intIndex <= 3; intIndex++)
        {
            pRstTitles->CursorType = 
               (enum CursorTypeEnum)aintCursorType[intIndex];
            pRstTitles->LockType = adLockOptimistic;

            // Pass the Cursor type and LockType to the Recordset.
            pRstTitles->Open ("Titles", strCnn, 
                (enum CursorTypeEnum)aintCursorType[intIndex], 
                adLockOptimistic, adCmdTable);

            switch(aintCursorType[intIndex])
            {
                case adOpenForwardOnly:
                    printf("\nForwardOnly cursor supports:\n");
                    break;

                case adOpenKeyset:
                    printf("\nKeyset cursor supports:\n");
                    break;

                case adOpenDynamic:
                    printf("\nDynamic cursor supports:\n");
                    break;

                case adOpenStatic:
                    printf("\nStatic cursor supports:\n");
                    break;

                default :
                    break;
            }

            DisplaySupport(pRstTitles);

            printf("\n\nPress any key to continue...");
            getch();

            //Clear the screen for the next display.
            system("cls");

            // Clean up objects before exit.
            pRstTitles->Close();
        }
    }

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

///////////////////////////////////////////////
//                                           //
//    DisplaySupport Function                //
//                                           //
///////////////////////////////////////////////
void DisplaySupport (_RecordsetPtr  pRstTemp)
{
    // Fill array with cursor option constants.
    long  alngConstants[11];
    alngConstants[0] = adAddNew;
    alngConstants[1] = adApproxPosition;
    alngConstants[2] = adBookmark;
    alngConstants[3] = adDelete;
    alngConstants[4] = adFind;
    alngConstants[5] = adHoldRecords;
    alngConstants[6] = adMovePrevious;
    alngConstants[7] = adNotify;
    alngConstants[8] = adResync;
    alngConstants[9] = adUpdate;
    alngConstants[10] = adUpdateBatch;

    for(int intIndex=0; intIndex <= 10; intIndex++)
    {
        bool booSupports = pRstTemp->
            Supports( (enum CursorOptionEnum)alngConstants[intIndex] );

        if(booSupports)
        {
            switch(alngConstants[intIndex])
            {
                case adAddNew :
                    printf("\n  AddNew");
                    break;

                case adApproxPosition :
                    printf("\n  AbsolutePosition and AbsolutePage");
                    break;

                case adBookmark :
                    printf("\n  Bookmark");
                    break;

                case adDelete :
                    printf("\n  Delete");
                    break;

                case adFind :
                    printf("\n  Find");
                    break;

                case adHoldRecords :
                    printf("\n  Holding Records");
                    break;

                case adMovePrevious :
                    printf("\n  MovePrevious and Move");
                    break;

                case adNotify :
                    printf("\n  Notifications");
                    break;

                case adResync :
                    printf("\n  Resyncing data");
                    break;

                case adUpdate :
                    printf("\n  Update");
                    break;

                case adUpdateBatch :
                    printf("\n  Batch updating");
                    break;

                default :
                    break;
            }
        }
    }
}

///////////////////////////////////////////////
//                                           //
//    PrintProviderError Function            //
//                                           //
///////////////////////////////////////////////
void PrintProviderError(_ConnectionPtr pConnection)
{
    // Print Provider Errors from Connection object.
    // pErr is a record object in the Connection’s Errors 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("Error number: %x\t%s\n", 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);
}