Die Eigenschaften ActualSize und DefinedSize – Beispiel (VC++)
In diesem Beispiel werden die Eigenschaften ActualSize und DefinedSize verwendet, um die definierte und die tatsächliche Größe eines Felds anzuzeigen.
Beispiel
// BeginActualSizeCpp.cpp
// compile with: /EHsc
#import "msado15.dll" no_namespace rename("EOF", "EndOfFile")
#include <ole2.h>
#include <stdio.h>
#include "conio.h"
// Function declarations
inline void TESTHR(HRESULT x) { if FAILED(x) _com_issue_error(x); };
void ActualSizeX();
void PrintProviderError(_ConnectionPtr pConnection);
int main() {
if (FAILED(::CoInitialize(NULL)))
return -1;
ActualSizeX();
::CoUninitialize();
}
void ActualSizeX() {
HRESULT hr = S_OK;
// Define ADO object pointers. Initialize pointers on define.
// These are in the ADODB:: namespace.
_RecordsetPtr pRstStores = NULL;
// Define Other variables
_bstr_t strMessage;
_bstr_t strCnn("Provider='sqloledb'; Data Source='My_Data_Source'; Initial Catalog='pubs'; Integrated Security='SSPI';");
try {
// Open a recordset for the stores table.
TESTHR(pRstStores.CreateInstance(__uuidof(Recordset)));
// You have to explicitly pass the Cursor type and LockType to the Recordset here.
hr = pRstStores->Open("stores", strCnn, adOpenForwardOnly, adLockReadOnly, adCmdTable);
// Loop through the recordset displaying the contents of the stor_name field,
// the field's defined size, and its actual size.
pRstStores->MoveFirst();
while (!(pRstStores->EndOfFile)) {
strMessage = "Store Name: ";
strMessage += (_bstr_t)pRstStores->Fields->Item["stor_name"]->Value + "\n";
strMessage += "Defined Size: ";
strMessage += (_bstr_t)pRstStores->Fields->Item["stor_name"]->DefinedSize + "\n";
strMessage += "Actual Size: ";
strMessage += (_bstr_t) pRstStores->Fields->Item["stor_name"]->ActualSize + "\n";
printf("%s\n",(LPCSTR)strMessage);
pRstStores->MoveNext();
}
}
catch(_com_error &e) {
_variant_t vtConnect = pRstStores->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 occurred.");
break;
}
}
// Clean up objects before exit.
if (pRstStores)
if (pRstStores->State == adStateOpen)
pRstStores->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;
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("\t Error number: %x\t%s", pErr->Number,(LPCSTR ) pErr->Description);
}
}
}
Store Name: Eric the Read Books
Defined Size: 40
Actual Size: 19
Store Name: Barnum's
Defined Size: 40
Actual Size: 8
Store-Name: News & Brews
Defined Size: 40
Actual Size: 12
Store Name: Doc-U-Mat: Quality Laundry and Books
Defined Size: 40
Actual Size: 36
Store Name: Fricative Bookshop
Defined Size: 40
Actual Size: 18
Store Name: Bookbeat
Defined Size: 40
Actual Size: 8