Utilizzo degli oggetti errore OLE DB (SQL Server Compact)
Quando si verificano errori durante l'esecuzione di un'applicazione basata su SQL Server Compact 3.5, il provider OLE DB per SQL Server Compact 3.5 restituisce e archivia una matrice di oggetti errore, ai quali è possibile accedere utilizzando OLE DB nel modo consueto. Il provider OLE DB per SQL Server Compact 3.5 restituisce errori per ogni interfaccia supportata dal provider. Per ulteriori informazioni, vedere Interfacce OLE DB implementate (SQL Server Compact). Per informazioni sul meccanismo generale applicato da un client OLE DB per recuperare informazioni sull'errore, vedere la sezione relativa a Microsoft OLE DB nella documentazione del kit SDK di Microsoft Data Access Components (MDAC), disponibile in MSDN Library.
Esempi
Nell'esempio seguente viene descritto come recuperare i numeri di errore specifici del provider quando si utilizza il provider OLE DB per SQL Server Compact 3.5.
Nota
Per eseguire l'applicazione di esempio, è necessario registrare sqlceoledb35.dll. È possibile registrare sqlceoledb35.dll in Windows da una riga di comando con l'utilità regsvr32.
Nota
CLSID_SQLSERVERCE è una macro definita nel file di intestazione OLE DB che esegue il mapping a CLSID_SQLSERVERCE_3_5.
#include <windows.h>
#include <sqlce_oledb.h>
#include <sqlce_err.h>
#include <stdio.h>
/// <summary>
/// This function demonstrates a routine that can handle and display
/// errors from the OLE DB provider for SQL Server Compact 3.5. The
/// errors that occured on the current thread are displayed.
/// </summary>
HRESULT DisplayCurrentThreadErrors()
{
static TCHAR *sErrIErrorInfo = L"IErrorInfo interface";
static TCHAR *sErrIErrorRecords = L"IErrorRecords interface";
static TCHAR *sErrRecordCount = L"error record count";
static TCHAR *sErrInfo = L"ERRORINFO structure";
static TCHAR *sErrStandardInfo = L"standard error info";
static TCHAR *sErrDescription = L"standard error description";
static TCHAR *sErrNoSource = L"error source";
HRESULT hr = S_OK;
IErrorInfo *pIErrorInfo = NULL;
IErrorRecords *pIErrorRecords = NULL;
ERRORINFO errorInfo = { 0 };
IErrorInfo *pIErrorInfoRecord = NULL;
try
{
// This interface supports returning error information.
// Get the error object from the system for the current
// thread.
hr = GetErrorInfo(0, &pIErrorInfo);
if ( hr == S_FALSE )
{
wprintf(L"No error occured.\n");
return S_OK;
}
if(FAILED(hr) || NULL == pIErrorInfo)
throw sErrIErrorInfo;
// The error records are retrieved from the IIErrorRecords
// interface, which can be obtained from the IErrorInfo
// interface.
hr = pIErrorInfo->QueryInterface(IID_IErrorRecords,
(void **) &pIErrorRecords);
if ( FAILED(hr) || NULL == pIErrorRecords )
throw sErrIErrorRecords;
// The IErrorInfo interface is no longer required because
// we have the IErrorRecords interface, relase it.
pIErrorInfo->Release();
pIErrorInfo = NULL;
ULONG ulNumErrorRecs = 0;
// Determine the number of records in this error object
hr = pIErrorRecords->GetRecordCount(&ulNumErrorRecs);
if ( FAILED(hr) )
throw sErrRecordCount;
// Loop over each error record in the error object to display
// information about each error. Errors are returned.
for (DWORD dwErrorIndex = 0;
dwErrorIndex < ulNumErrorRecs;
dwErrorIndex++)
{
// Retrieve basic error information for this error.
hr = pIErrorRecords->GetBasicErrorInfo(dwErrorIndex,
&errorInfo);
if ( FAILED(hr) )
throw sErrInfo;
TCHAR szCLSID[64] = { 0 };
TCHAR szIID[64] = { 0 };
TCHAR szDISPID[64] = { 0 };
StringFromGUID2(errorInfo.clsid, (LPOLESTR)szCLSID,
sizeof(szCLSID));
StringFromGUID2(errorInfo.iid, (LPOLESTR)szIID,
sizeof(szIID));
wprintf(L"HRESULT = %lx\n", errorInfo.hrError);
wprintf(L"clsid = %s\n", szCLSID);
wprintf(L"iid = %s\n", szIID);
wprintf(L"dispid = %ld\n", errorInfo.dispid);
wprintf(L"Native Error Code = %lx\n", errorInfo.dwMinor);
// Retrieve standard error information for this error.
hr = pIErrorRecords->GetErrorInfo(dwErrorIndex, NULL,
&pIErrorInfoRecord);
if ( FAILED(hr) )
throw sErrStandardInfo;
BSTR bstrDescriptionOfError;
BSTR bstrSourceOfError;
// Get the description of the error.
hr = pIErrorInfoRecord->GetDescription(
&bstrDescriptionOfError);
if ( FAILED(hr) )
throw sErrDescription;
wprintf(L"Description = %s\n", bstrDescriptionOfError);
// Get the source of the error.
hr = pIErrorInfoRecord->GetSource(&bstrSourceOfError);
if ( FAILED(hr) )
throw sErrNoSource;
wprintf(L"Description = %s\n", bstrSourceOfError);
// This interface variable will be used the next time
// though this loop. In the last error case this interface
// is no longer needed so we must release it.
if(NULL != pIErrorInfoRecord)
pIErrorInfoRecord->Release();
pIErrorInfoRecord = NULL;
}
}
catch( TCHAR *szMsg )
{
wprintf(L"Failed to retrieve ");
wprintf(szMsg);
}
if( pIErrorInfoRecord )
pIErrorInfoRecord->Release();
if ( pIErrorInfo )
pIErrorInfo->Release();
if ( pIErrorRecords )
pIErrorRecords->Release();
return hr;
}
/// <summary>
/// This called will try to connect to a non existant
/// database to cause an error condition so that the call
/// to DisplayCurrentThreadError() has some errors to
/// display.
/// </summary>
/// <param="pIDBProperties">
/// IDBProperties interface that is used to set the properties on
/// for the Sql Compact engine object.
/// </param>
/// <param="pIDBInitialize">
/// Interface to the Sql Compact initialization object.
/// </param>
void CreateErrorCondition(IDBProperties *pIDBProperties,
IDBInitialize *pIDBInitialize)
{
HRESULT hr = S_OK;
DBPROP dbprop[1];
DBPROPSET dbpropset[1];
VariantInit(&dbprop[0].vValue);
// Initialize a property that uses name of database.
dbprop[0].dwPropertyID = DBPROP_INIT_DATASOURCE;
dbprop[0].dwOptions = DBPROPOPTIONS_REQUIRED;
dbprop[0].vValue.vt = VT_BSTR;
dbprop[0].vValue.bstrVal = SysAllocString(L"t@#$94.SC5");
// Initialize the property set.
dbpropset[0].guidPropertySet = DBPROPSET_DBINIT;
dbpropset[0].rgProperties = dbprop;
dbpropset[0].cProperties = sizeof(dbprop)/sizeof(dbprop[0]);
hr = pIDBProperties->SetProperties(
sizeof(dbpropset)/sizeof(dbpropset[0]),
dbpropset);
VariantClear(&dbprop[0].vValue);
if( FAILED(hr) )
return;
SysFreeString(dbprop[0].vValue.bstrVal);
// This call will fail because the db does not exit.
pIDBInitialize->Initialize();
}
/// <summary>
/// Application entry point initializes and cleans up the
/// needed interfaces and then calls the
/// DisplayCurrentThreadErrors() function to display error
/// information for the main application thread.
/// </summary>
void main()
{
HRESULT hr = S_OK;
IDBProperties *pIDBProperties = NULL;
ISupportErrorInfo *pISupportErrorInfo = NULL;
IDBInitialize *pIDBInitialize = NULL;
BOOL bComInitialized = FALSE;
try
{
hr = CoInitialize(NULL);
if ( FAILED(hr) )
{
wprintf(L"CoInitialize failed");
throw hr;
}
bComInitialized = TRUE;
// Retrieve the SQL Compact edition initialization interface.
hr = CoCreateInstance(CLSID_SQLSERVERCE,
0,
CLSCTX_INPROC_SERVER,
IID_IDBInitialize,
(void**)&pIDBInitialize);
if( FAILED(hr) || NULL == pIDBInitialize )
{
wprintf(L"Failed to retrieve IDBInitialize Interface");
throw hr;
}
// Retrieve the property interface, This interface will enable
// setting of specific propertes on the SQL Server Compact
// engine object.
hr = CoCreateInstance(CLSID_SQLSERVERCE,
0,
CLSCTX_INPROC_SERVER,
IID_IDBProperties,
(void**) &pIDBProperties);
if( FAILED(hr) || NULL == pIDBProperties )
{
wprintf(L"Failed to retrieve IDBProperties Interface");
throw hr;
}
hr = pIDBProperties->QueryInterface(IID_ISupportErrorInfo,
(void**)&pISupportErrorInfo);
if( FAILED(hr) || NULL == pISupportErrorInfo )
{
wprintf(L"Interface does not support ISupportErrorInfo");
throw hr;
}
// Create an error condition by trying to open a non existance
// datafile.
CreateErrorCondition(pIDBProperties, pIDBInitialize);
// Display errors that occured on the current (main) thread.
hr = DisplayCurrentThreadErrors();
if ( FAILED(hr) )
throw hr;
}
catch( HRESULT hr)
{
wprintf(L", Error Code: %lx\n", hr);
}
if ( pISupportErrorInfo )
pISupportErrorInfo->Release();
if ( pIDBProperties )
pIDBProperties->Release();
if ( pIDBInitialize )
pIDBInitialize->Release();
if ( bComInitialized )
CoUninitialize();
}
Vedere anche
Riferimento
Guida di riferimento al provider OLE DB (SQL Server Compact)