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.cpp
// compile with: /EHsc
#import "msado15.dll" no_namespace rename("EOF", "EndOfFile")
#include <stdio.h>
#include <ole2.h>
#include <conio.h>
#include <string.h>
#include "icrsint.h"
// 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;
};
// Function declarations
inline void TESTHR(HRESULT x) { if FAILED(x) _com_issue_error(x); };
void SeekX();
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;
}
int main() {
if (FAILED(::CoInitialize(NULL)))
return -1;
SeekX();
::CoUninitialize();
}
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_s(strEmpId," \t", NULL);
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 occurred.");
break;
}
}
// Clean up objects before exit. Release the IADORecordset Interface here
if (picRs)
picRs->Release();
if (pRstEmp)
if (pRstEmp->State == adStateOpen)
pRstEmp->Close();
}
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);
}
}
}
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);
}