fail to enumerate putput pins in Async File Reader

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C++

MFC

COM

directshow

i have added a source filter to graph ,now i need to conect filters individually.
at first , i need to retrive the source filter output pins .

i used this funtion to enumerate the pin but at the pEnum->Next(1, &pPin, NULL)
the pEnum return S_FALSE.
but HRESULT hr = pFilter->EnumPins(&pEnum); the hr =S_OK.
i have no idea about this .may i have lose any thing before call this funtion
and i have tried another source filter (AVI/WAV File Source)in GetUnconnectedPin funtion but it fails again.

HRESULT GetUnconnectedPin(
    IBaseFilter *pFilter,   // Pointer to the filter.
    PIN_DIRECTION PinDir,   // Direction of the pin to find.
    IPin **ppPin)           // Receives a pointer to the pin.
{
    *ppPin = 0;
    IEnumPins *pEnum = 0;
    IPin *pPin = 0;
    HRESULT hr = pFilter->EnumPins(&pEnum);
    if (FAILED(hr))
    {
        return hr;
    }
   //it works very good untill here
    while (pEnum->Next(1, &pPin, NULL) == S_OK)//here ,pEnum return S_FALSE
    {
        PIN_DIRECTION ThisPinDir;
        pPin->QueryDirection(&ThisPinDir);
        if (ThisPinDir == PinDir)
        {
            IPin *pTmp = 0;
            hr = pPin->ConnectedTo(&pTmp);
            if (SUCCEEDED(hr))  // Already connected, not the pin we want.
            {
                pTmp->Release();
            }
            else  // Unconnected, this is the pin we want.
            {
                pEnum->Release();
                *ppPin = pPin;
                return S_OK;
            }
        }
        pPin->Release();
    }
    pEnum->Release();
    // Did not find a matching pin.
    return E_FAIL;
}

[EDIT] Added pre tags for better readability - Code-o-mat [/EDIT]