Connection Close Method, Table Type Property Example (VC++)

Setting the ActiveConnection property to Nothing should "close" the catalog. Associated collections will be empty. Any objects that were created from schema objects in the catalog will be orphaned. Any properties on those objects that have been cached will still be available, but attempting to read properties that require a call to the provider will fail.

// BeginCloseConnectionCpp.cpp  
// compile with: /EHsc  
#import "msado15.dll" rename("EOF", "EndOfFile")  
#import "msadox.dll" no_namespace  
  
#include "iostream"  
using namespace std;  
  
// Function declarations  
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);};  
void CloseConnectionByNothingX();  
void CloseConnectionX();  
  
int main() {  
   if ( FAILED(::CoInitialize(NULL) ) )  
      return -1;  
  
   CloseConnectionByNothingX();  
   CloseConnectionX();  
  
   ::CoUninitialize();  
}  
  
void CloseConnectionByNothingX() {  
   HRESULT hr = S_OK;  
  
   // Define and initialize ADOX object pointers, in ADODB namespace.  
   _CatalogPtr m_pCatalog = NULL;  
   _TablePtr m_pTable = NULL;  
  
   // Define ADODB object pointers  
   ADODB::_ConnectionPtr m_pCnn = NULL;  
  
   // Define other variables  
   _variant_t vIndex = (short) 0;  
  
   try {  
      TESTHR(hr = m_pCnn.CreateInstance(__uuidof(ADODB::Connection)));  
      TESTHR(hr = m_pCatalog.CreateInstance(__uuidof(Catalog)));  
  
      m_pCnn->Open("Provider='Microsoft.JET.OLEDB.4.0';Data Source= 'c:\\Northwind.mdb';", "", "", NULL);  
      m_pCatalog->PutActiveConnection(_variant_t((IDispatch *)m_pCnn));  
      m_pTable = m_pCatalog->Tables->GetItem(vIndex);  
  
      // Cache m_pTable.Type info  
      cout << m_pTable->Type << endl;  
  
      _variant_t vCnn;  
      vCnn.vt = VT_DISPATCH;  
      vCnn.pdispVal = NULL;  
      m_pCatalog->PutActiveConnection(vCnn);  
  
      // m_pTable is orphaned, will succeed if this was cached  
      cout << m_pTable->Type << endl;  
  
      cout << m_pTable->Columns->GetItem(vIndex)->DefinedSize << endl;  
      // Previous line will fail if this info has not been cached  
   }  
   catch(_com_error &e) {  
      // Notify the user of errors if any.  
      _bstr_t bstrSource(e.Source());  
      _bstr_t bstrDescription(e.Description());  
  
      printf("\nError\n\tSource :  %s \n\tdescription : %s \n", (LPCSTR)bstrSource, (LPCSTR)bstrDescription);  
   }  
   catch(...) {  
      cout << "Error occurred in CloseConnectionByNothingX...." << endl;  
   }  
}  
  
void CloseConnectionX() {  
   HRESULT hr = S_OK;  
  
   // Define ADOX object pointers, initialize pointers. These are in ADODB  namespace.  
  
   _CatalogPtr m_pCatalog = NULL;  
   _TablePtr m_pTable = NULL;  
  
   // Define ADODB object pointers  
   ADODB::_ConnectionPtr m_pCnn = NULL;  
  
   // Define other variables  
   _variant_t vIndex = (short) 0;  
   try {  
      TESTHR(hr = m_pCnn.CreateInstance(__uuidof(ADODB::Connection)));  
      m_pCnn->Open("Provider='Microsoft.JET.OLEDB.4.0';Data Source= 'c:\\Northwind.mdb';", "", "", NULL);  
  
      TESTHR(hr = m_pCatalog.CreateInstance(__uuidof(Catalog)));  
      m_pCatalog->PutActiveConnection(_variant_t((IDispatch *)m_pCnn));  
  
      m_pTable = m_pCatalog->Tables->GetItem(vIndex);  
  
      // Cache m_pTable.Type info  
      cout << m_pTable->Type << endl;  
  
      m_pCnn->Close();  
  
      // m_pTable is orphaned, will succeed if this was cached  
      cout << m_pTable->Type << endl;  
  
      cout << m_pTable->Columns->GetItem(vIndex)->DefinedSize << endl;  
      // Previous line will fail if this info has not been cached  
   }  
   catch(_com_error &e) {  
      // Notify the user of errors if any.  
      _bstr_t bstrSource(e.Source());  
      _bstr_t bstrDescription(e.Description());  
  
      printf("\nError\n\tSource :  %s \n\tdescription : %s \n", (LPCSTR)bstrSource, (LPCSTR)bstrDescription);  
   }  
   catch(...) {  
      cout << "Error occurred in CloseConnectionX...." << endl;  
   }  
}  

See Also

ActiveConnection Property (ADOX)