Seek Method and Index Property Example (VC++)

This example uses the Recordset object's Seek method and Index property in conjunction with a given Employee ID, to locate the employee's name in the Employees table of the Nwind.mdb database.

// BeginSeekCpp
#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 <string.h>
#include "SeekX.h"

//Function declarations
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);};
void SeekX(void);
void PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);
inline char* mygets(char* strDest, int n) 
{    
    char strExBuff[10];
    char* pstrRet = fgets(strDest, n, stdin);

    if (pstrRet == NULL)
        return NULL;

    if (!strrchr(strDest, '\n'))
        // Exhaust the input buffer.
        do
        {
            fgets(strExBuff, sizeof(strExBuff), stdin);
        }while (!strrchr(strExBuff, '\n'));
    else
        // Replace '\n' with '\0'
        strDest[strrchr(strDest, '\n') - strDest] = '\0';

    return pstrRet;
}

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

    SeekX();

    ::CoUninitialize();
}

//////////////////////////////////////////////////////////
//                                                      //
//     SeekX Function                                   //
//                                                      //
//////////////////////////////////////////////////////////
void SeekX()
{
    HRESULT hr = S_OK;

    // Define ADO object pointers.
    // Initialize pointers on define.
    // These are in the ADODB::  namespace.

    _RecordsetPtr pRstEmp = NULL;

    IADORecordBinding    *picRs = NULL;  // Interface Pointer declared
    CEmployeeRs EmpRs; //C++ class object

    //Definitions of other variables
    _bstr_t strPrompt("Enter an EmployeeID (e.g., 1 to 9)");
    char strEmpId[2];

    try
    {
        TESTHR(pRstEmp.CreateInstance(__uuidof(Recordset)));
        pRstEmp->CursorLocation = adUseServer;
        pRstEmp->Open("employees", "Provider='Microsoft.Jet.OLEDB.4.0';" 
            "Data Source='C:\\Program Files\\Microsoft Office\\Office\\"
            "Samples\\Northwind.mdb';",
            adOpenKeyset,adLockReadOnly,adCmdTableDirect);

        //Open an IADORecordBinding interface pointer which 
        //we'll use for binding Recordset to a Class  
        TESTHR(pRstEmp->QueryInterface(
            __uuidof(IADORecordBinding), (LPVOID*)&picRs));

        //Bind the Recordset to a C++ Class
        TESTHR(picRs->BindToRecordset(&EmpRs));

        //Does this provider support Seek and Index?
        if (pRstEmp->Supports(adIndex) && pRstEmp->Supports(adSeek))
        {
            pRstEmp->Index = "PrimaryKey";

            //Display all the employees.
            pRstEmp->MoveFirst();
            while (!pRstEmp->EndOfFile)
            {
                  printf("%d : %s %s\n",  
                      EmpRs.le_empidStatus == adFldOK ? 
                      EmpRs.m_ie_empid : 0, 
                      EmpRs.le_fnameStatus == adFldOK ? 
                      EmpRs.m_sze_fname : "<NULL>", 
                      EmpRs.le_lnameStatus == adFldOK ? 
                      EmpRs.m_sze_lname : "<NULL>");

                  pRstEmp->MoveNext();
            }
            //Prompt the user for an EmployeeID between 1 and 9.
            do
            {
                pRstEmp->MoveFirst();
                printf("\n\n%s\t",(LPCSTR) strPrompt);
                mygets(strEmpId, 2);

                //Quit if strEmpID is a zero-length string 
                //(CANCEL, null, etc.)
                char *strTemp = strtok(strEmpId," \t");
                if (strTemp == NULL) break;
                if (strlen(strTemp) == 1 && atoi(strTemp) >= 1 && 
                    atoi(strTemp) <= 9)
                {
                    _variant_t strEmployeeId(strTemp);
                    pRstEmp->Seek(strEmployeeId, adSeekAfterEQ);
                    if (pRstEmp->EndOfFile)
                    {
                        printf("Employee not found.\n");
                    }
                    else
                    {
                        printf("%d : Employee='%s %s'\n",  
                            EmpRs.le_empidStatus == adFldOK ? 
                            EmpRs.m_ie_empid : 0,
                            EmpRs.le_fnameStatus == adFldOK ? 
                            EmpRs.m_sze_fname : "<NULL>", 
                            EmpRs.le_lnameStatus == adFldOK ? 
                            EmpRs.m_sze_lname : "<NULL>");
                    }
                }
            }
            while(true);
        }  
    }
    catch(_com_error &e)
    {
       // Notify the user of errors if any.
       // Pass a connection pointer accessed from the Recordset.
        _variant_t vtConnect = pRstEmp->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.
    //Release the IADORecordset Interface here   
    if (picRs)
        picRs->Release();
        
    if (pRstEmp)
        if (pRstEmp->State == adStateOpen)
            pRstEmp->Close();
}

///////////////////////////////////////////////////////////
//                                                       //
//      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);
}
// EndSeekCpp

SeekX.h

// BeginSeekH
#include "icrsint.h"

// This Class extracts only EmployeeId,FirstName and LastName
// from employees table
class CEmployeeRs : public CADORecordBinding
{
BEGIN_ADO_BINDING(CEmployeeRs)
    
   // Column hiredate is the 1st field in the table.
   ADO_VARIABLE_LENGTH_ENTRY2(1, adInteger,m_ie_empid, 
        sizeof(m_ie_empid), le_empidStatus, FALSE)

    // Column LastName is the 2nd field in the table.
   ADO_VARIABLE_LENGTH_ENTRY2(2, adVarChar, m_sze_lname, 
         sizeof(m_sze_lname), le_lnameStatus, FALSE)

    // Column FirstName is the 3rd field in the table.
   ADO_VARIABLE_LENGTH_ENTRY2(2, adVarChar, m_sze_fname, 
         sizeof(m_sze_fname), le_fnameStatus, FALSE)
END_ADO_BINDING()

public:
   INT    m_ie_empid;
   ULONG  le_empidStatus;
   CHAR    m_sze_fname[11];
   ULONG  le_fnameStatus;
   CHAR    m_sze_lname[21];
   ULONG  le_lnameStatus;    
};
// EndSeekH

See Also

Index Property | Recordset Object | Seek Method