---
title: "Visual C++ Extensions Example | Microsoft Docs"
ms.prod: sql
ms.prod_service: connectivity
ms.technology: connectivity
ms.custom: ""
ms.date: 11/08/2018
ms.reviewer: ""
ms.topic: conceptual
dev_langs: 
  - "C++"
helpviewer_keywords: 
  - "ADO, Visual C++"
  - "Visual C++ [ADO], VC++ extensions example"
ms.assetid: 9739c278-582c-402b-a158-7f68a1b2c293
author: MightyPen
ms.author: genemi
---
# Visual C++ Extensions Example
This program shows how values are retrieved from fields and converted to C/C++ variables.  
  
 This example also takes advantage of "smart pointers," which automatically handle the COM-specific details of calling `QueryInterface` and reference counting for the **IADORecordBinding** interface.  
  
 Without smart pointers, you would code:  
  
```cpp
IADORecordBinding   *picRs = NULL;  
...  
TESTHR(pRs->QueryInterface(  
          __uuidof(IADORecordBinding), (LPVOID*)&picRs));  
...  
if (picRs) picRs->Release();  
```  
  
 With smart pointers, you derive the `IADORecordBindingPtr` type from the `IADORecordBinding` interface with this statement:  
  
```cpp
_COM_SMARTPTR_TYPEDEF(IADORecordBinding, __uuidof(IADORecordBinding));  
```  
  
 And instantiate the pointer like this:  
  
```cpp
IADORecordBindingPtr picRs(pRs);  
```  
  
 Because the Visual C++ Extensions are implemented by the **Recordset** object, the constructor for the smart pointer, `picRs`, takes the _`RecordsetPtr` pointer, `pRs`. The constructor calls `QueryInterface` using `pRs` to find the `IADORecordBinding` interface.  
  
```cpp
// Visual_Cpp_Extensions_Example.cpp  
// compile with: /EHsc  
#import "msado15.dll" no_namespace rename("EOF", "EndOfFile")  
  
#include <icrsint.h>  
_COM_SMARTPTR_TYPEDEF(IADORecordBinding, __uuidof(IADORecordBinding));  
  
inline void TESTHR(HRESULT _hr) { if FAILED(_hr) _com_issue_error(_hr); }  
  
class CCustomRs : public CADORecordBinding {  
   BEGIN_ADO_BINDING(CCustomRs)  
      ADO_VARIABLE_LENGTH_ENTRY2(2, adVarChar, m_ch_fname, sizeof(m_ch_fname), m_ul_fnameStatus, false)  
      ADO_VARIABLE_LENGTH_ENTRY2(4, adVarChar, m_ch_lname, sizeof(m_ch_lname), m_ul_lnameStatus, false)  
   END_ADO_BINDING()  
  
public:  
   CHAR m_ch_fname[22];  
   CHAR m_ch_lname[32];  
   ULONG m_ul_fnameStatus;  
   ULONG m_ul_lnameStatus;  
};  
  
int main() {  
   ::CoInitialize(NULL);  
   try {  
      _RecordsetPtr pRs("ADODB.Recordset");  
      CCustomRs rs;  
      IADORecordBindingPtr picRs(pRs);  
  
      pRs->Open(L"SELECT * FROM Employee ORDER BY lname", L"dsn=DataPubs;Trusted_Connection=yes;", adOpenStatic, adLockOptimistic, adCmdText);  
  
      TESTHR(picRs->BindToRecordset(&rs));  
  
      while (!pRs->EndOfFile) {  
         // Process data in the CCustomRs C++ instance variables.  
         printf("Name = %s %s\n",  
            (rs.m_ul_fnameStatus == adFldOK ? rs.m_ch_fname: "<Error>"),   
            (rs.m_ul_lnameStatus == adFldOK ? rs.m_ch_lname: "<Error>") );  
  
         // Move to the next row of the Recordset.   Fields in the new row will   
         // automatically be placed in the CCustomRs C++ instance variables.  
  
         pRs->MoveNext();  
      }  
   }  
   catch (_com_error &e ) {  
      printf("Error:\n");  
      printf("Code = %08lx\n", e.Error());  
      printf("Meaning = %s\n", e.ErrorMessage());  
      printf("Source = %s\n", (LPCSTR) e.Source());  
      printf("Description = %s\n", (LPCSTR) e.Description());  
   }  
   ::CoUninitialize();  
}  
```  
  
## See Also  
 [Using Visual C++ Extensions](../../../ado/guide/appendixes/using-visual-c-extensions.md)   
 [Visual C++ Extensions Header](../../../ado/guide/appendixes/visual-c-extensions-header.md)