初始化裝置屬性的程式碼範例

在 Root 項目的 IWiaMiniDrv::drvInitItemProperties 呼叫期間，微型驅動程式必須初始化下列描述裝置的 WIA 屬性：

WIA_DPS_SERVICE_ID

WIA_DPS_DEVICE_ID

WIA_DPS_GLOBAL_IDENTITY

WIA_DPA_FIRMWARE_VERSION

下列程式碼範例示範如何使用 OpenPropertyStore 和 ReadDeviceProperty 方法來初始化WIA_DPS_SERVICE_ID，以讀取PKEY_PNPX_ServiceId。 相同的一般方法可用來初始化每個裝置屬性。

HRESULT hr = S_OK;
IPropertyStore *pPropertyStore = NULL;
BSTR bstrPropertyValue = NULL;

//
// Open the current Property Store and keep it opened until all needed properties are read
//
if (SUCCEEDED(hr))
{
    hr = OpenPropertyStore(&pPropertyStore);
    if (FAILED(hr))
    {
        WIAS_ERROR((g_hInst, "Failed to open the Property Store for the current Function Instance, hr = 0x%08X", hr));
    }
}

//
// Initialize WIA_DPS_SERVICE_ID
//
if (SUCCEEDED(hr))
{
    hr = ReadDeviceProperty(pPropertyStore, &PKEY_PNPX_ServiceId, &bstrPropertyValue);
    if (FAILED(hr))
    {
        WIAS_ERROR((g_hInst, "Failed to read the PKEY_PNPX_ServiceId device property, hr = 0x%08X", hr));
    }

    if ((SUCCEEDED(hr)) && (bstrPropertyValue)) 
    {
        WIAS_TRACE((g_hInst, "Service id: %ws", (LPWSTR)bstrPropertyValue));
 
        hr = AddProperty(WIA_DPS_SERVICE_ID, WIA_DPS_SERVICE_ID_STR, RN, bstrPropertyValue);
        if (FAILED(hr)) 
        {
            WIAS_ERROR((g_hInst, "Failed to add WIA_DPS_SERVICE_ID property to the property manager, hr = 0x%08X", hr));
        }
    }

    if (bstrPropertyValue)
    {
        SysFreeString(bstrPropertyValue);
        bstrPropertyValue = NULL;
    }
}

//
// Repeat the same procedure for WIA_DPS_DEVICE_ID, WIA_DPS_GLOBAL_IDENTITY, and WIA_DPS_FIRMWARE_VERSION
//

//
// Close the Property Store
//
if (pPropertyStore)
{
    pPropertyStore->Release();
    pPropertyStore = NULL;
}