Step 9. Working With Extension Properties

In this step you will learn how server extension settings can be stored and configured by a user. Server extension must implement IPersistPropertyBag to take benefits of this approach. Server extension will use its configuration to read the path to the database it uses, and till this step it used hard-coded path.

1. Add line

public IPersistPropertyBag

to the list of classes CMyFirst inherits from. Find CMyFirst class definition, and its first lines should be

class ATL_NO_VTABLE CMyFirst : 
	public CComObjectRootEx<CComMultiThreadModel>,
	public CComCoClass<CMyFirst, &CLSID_MyFirst>,
	public ISupportErrorInfo,
	public IMyFirst,
	public ICommonExtender,
	public ICommonAuthentication,
	public IRADIUSAuthentication,
	public IRADIUSAccounting,
	public ITACACSAccounting,
	public IRADIUSAuthorization,
	public ITACACSAuthorization,
	public IPersistPropertyBag
{

Add line

COM_INTERFACE_ENTRY(IPersistPropertyBag)

to the interface map.

2. Add private CMyFirst member

_bstr_t m_DBPath;

It will store value read from extension configuration.

3. Add lines

BEGIN_CATEGORY_MAP(CServerExtension)
	IMPLEMENTED_CATEGORY(CATID_TACRADServerExtension)
END_CATEGORY_MAP()

before interface map. These lines declare that server extension implements special COM category so Server Manager can find it within registered COM servers. Add directive

#include "..\ext_category.h"

after line

#include "Database.h"

5. Add the following lines of code to the public part of CMyFirst class definition:

STDMETHOD(Load)(IPropertyBag *pPropBag,IErrorLog *pErrorLog)
{
	VARIANT var;
	VariantInit(&var);
	if (SUCCEEDED(pPropBag->Read(L"DB Path",&var,pErrorLog)))
		m_DBPath=_bstr_t(var.bstrVal,false);
	return S_OK;
}
STDMETHOD(Save)(IPropertyBag *pPropBag, BOOL fClearDirty, 
	BOOL fSaveAllProperties)
{
	VARIANT var;
	VariantInit(&var);
	var.bstrVal=NULL;
	var.vt=VT_BSTR;
	pPropBag->Write(L"DB Path",&var);
	return S_OK;
}
STDMETHOD(GetClassID)(CLSID* pClsID)
{
	return E_NOTIMPL;
}
STDMETHOD(InitNew)()
{
	return E_NOTIMPL;
}

6. Now server extension will make use of m_DBPath variable we have created. Find Initialize method in CMyFirst class. Replace constant file path with M_DBPath variable, and method declaration must look so now:

 STDMETHOD(Initialize)(VARIANT_BOOL start)
{
	if (start==VARIANT_TRUE)
	{
		return m_DB.Open(m_DBPath);
	}
	else
		m_DB.Close();
	return S_OK;
}

Go to the next step.