使用

HRESULT AdviseFREngineObject( IUnknown* object, IUnknown* callback, DWORD* cookie );
HRESULT UnAdviseFREngineObject( IUnknown* object, DWORD cookie );
class CFRDocumentCallback: public IFRDocumentEvents {
public:
...
    // IUnknown メソッドの簡易実装
    ULONG STDMETHODCALLTYPE AddRef() { return 1; }
    ULONG STDMETHODCALLTYPE Release() { return 1; }
    HRESULT STDMETHODCALLTYPE QueryInterface( REFIID riid, void** ppObject )
    {
        if( ppObject == 0 ) {
            return E_POINTER;
        }
    *ppObject = 0;
    if( riid == IID_IUnknown || riid == IID_IFRDocumentEvents )
    {
        *ppObject = this;
        AddRef();
        return S_OK;
    } else {
        return E_NOINTERFACE;
    }
}
// IFRDocumentEvents メソッドの実装
HRESULT STDMETHODCALLTYPE OnProgress(
IFRDocument* sender, int percentage, VARIANT_BOOL* cancel );
HRESULT STDMETHODCALLTYPE OnWarning(
IFRDocument* sender, int index, BSTR tip, VARIANT_BOOL* cancel );
HRESULT STDMETHODCALLTYPE OnPageProcessed(
    IFRDocument* sender, int index, PageProcessingStageEnum stage ) { return S_OK; }
};
// FRDocument オブジェクトはすでに取得済みとします
IFRDocument* document;
// Callback オブジェクトを作成
CFRDocumentCallback callbackObject;
// リスナーを通知ソースに登録
DWORD cookie; // Advise メソッドから返される cookie を格納する変数
AdviseFREngineObject( frDocument, &callbackObject, &cookie );
// ドキュメントを処理
...
// 通知後はリスナーが不要になるため、登録を解除
UnadviseFREngineObject( frDocument, cookie );

Private WithEvents document As FREngine.FRDocument
Private Sub document_RecognitionOnProgress(ByVal sender As FREngine.FRDocument, _
                                           ByVal Percentage As Integer, _
                                           ByRef cancel As Boolean)
...
End Sub
Private Sub document_RecognitionOnProgress(ByVal sender As FREngine.FRDocument, _
                                           ByVal Percentage As Integer, _
                                           ByRef cancel As Boolean) Handles document.OnProgress
...
End Sub
document = Engine.CreateFRDocument
document.AddImageFile("D:\Demo.tif")
AddHandler document.OnProgress, AddressOf Me.document_RecognitionOnProgress
document.Process()
RemoveHandler document.OnProgress, AddressOf Me.document_RecognitionOnProgress
or simply use the FRDocument object for processing if you define the event handling methods with Handles keyword:
document = Engine.CreateFRDocument
document.AddImageFile("D:\Demo.tif")
document.Process()

class CFRDocumentEventsListener : public IFRDocumentEvents {
public:
...
    // IUnknown メソッドの簡易実装を提供します。これらは
    // COM サポートを持つ標準クラスを継承して実装することもできます
    ULONG AddRef();
    ULONG Release();
    HRESULT QueryInterface(REFIID riid, void** ppvObject)
    {
        if( ppvObject == 0 )
            return E_INVALIDARG;
        if( riid == __uuidof(IFRDocumentEvents) ) {
            *ppvObject = static_cast<IFRDocumentEvents*>( this );
        } else if( riid == IID_IUnknown ) {
            *ppvObject = static_cast<IUnknown*>( this );
        } else {
            *ppvObject = 0;
            return E_NOINTERFACE;
        }
        AddRef();
        return S_OK;
    }
    // IFRDocumentEvents メソッドを実装します
 HRESULT STDMETHODCALLTYPE OnProgress(
  IFRDocument* sender, int percentage, VARIANT_BOOL* cancel );
 HRESULT STDMETHODCALLTYPE OnWarning(
  IFRDocument* sender, int index, BSTR tip, VARIANT_BOOL* cancel );
 HRESULT STDMETHODCALLTYPE OnPageProcessed(
  IFRDocument* sender, int index, PageProcessingStageEnum stage ) { return S_OK; }
};
// FRDocument オブジェクトはすでに取得済みであるとします
IFRDocument* document;
// FRDocument オブジェクトに対して IConnectionPointContainer を照会します
IConnectionPointContainer* pContainer=0;
document->QueryInterface(IID_IConnectionPointContainer, (void**)&pContainer);
// connectable object 内の接続ポイントにある IConnectionPoint インターフェイスへのポインターを取得します
IConnectionPoint* pPoint=0;
pContainer->FindConnectionPoint(__uuidof(IFRDocumentEvents),
                                &pPoint);
// CFRDocumentEventsListener クラスと接続ポイントの間に接続を確立します
CFRDocumentEventsListener listener;
IUnknown* listenerUnknown=0;
listener.QueryInterface(IID_IUnknown, (void**)&listenerUnknown);
// 通知ソースに listener を advise します
DWORD cookie; // IConnectionPoint::Advise メソッドから返される cookie を格納する変数
pPoint->Advise(listenerUnknown, &cookie);
// ドキュメントを処理します
...
// 通知後は listener が不要になるため、advise を解除する必要があります
pPoint->Unadvise(cookie);

private void document_RecognitionOnProgress(FREngine.IFRDocument sender, int Percentage, ref bool cancel)
{
 ...
}
FREngine.DIFRDocumentEvents_OnProgressEventHandler recognizeOnProgressHandler =
 new FREngine.DIFRDocumentEvents_OnProgressEventHandler(
 document_RecognitionOnProgress );
document.OnProgress += recognizeOnProgressHandler;
document.Process( null, null, null );
document.OnProgress -= recognizeOnProgressHandler;