Called by the Windows Biometric Framework to return results from the asynchronous WinBioLocateSensorWithCallback function. The client application must implement this function.

Important  We recommend that, beginning with Windows 8, you no longer use the PWINBIO_LOCATE_SENSOR_CALLBACK/WinBioLocateSensorWithCallback combination. Instead, do the following:
  • Implement a PWINBIO_ASYNC_COMPLETION_CALLBACK function to receive notice when the operation completes.
  • Call the WinBioAsyncOpenSession function. Pass the address of your callback in the CallbackRoutine parameter. Pass WINBIO_ASYNC_NOTIFY_CALLBACK in the NotificationMethod parameter. Retrieve an asynchronous session handle.
  • Use the asynchronous session handle to call WinBioLocateSensor. When the operation finishes, the Windows Biometric Framework will allocate and initialize a WINBIO_ASYNC_RESULT structure with the results and invoke your callback with a pointer to the results structure.
  • Call WinBioFree from your callback implementation to release the WINBIO_ASYNC_RESULT structure after you have finished using it.


  _In_opt_ PVOID          LocateCallbackContext,
  _In_     HRESULT        OperationStatus,
           WINBIO_UNIT_ID UnitId


LocateCallbackContext [in, optional]

Pointer to a buffer defined by the application and passed to the LocateCallbackContext parameter of the WinBioLocateSensorWithCallback function. The buffer is not modified by the framework or the biometric unit. Your application can use the data to help it determine what actions to perform or to maintain additional information about the biometric capture.

OperationStatus [in]

Error code returned by the capture operation.


Biometric unit ID number.

Return value

Do not return a value from your implementation of this function.


The following function calls WinBioLocateSensorWithCallback to locate biometric sensor. The WinBioLocateSensorWithCallback is an asynchronous function that configures the biometric subsystem to locate the sensor on another thread. Output from the biometric subsystem is sent to a custom callback function named LocateSensorCallback. Link to the Winbio.lib static library and include the following header files:

  • Windows.h
  • Stdio.h
  • Conio.h
  • Winbio.h

HRESULT LocateSensorWithCallback(BOOL bCancel)
    HRESULT hr = S_OK;
    WINBIO_UNIT_ID unitId = 0;

    // Connect to the system pool. 
    hr = WinBioOpenSession( 
            WINBIO_TYPE_FINGERPRINT,    // Service provider
            WINBIO_POOL_SYSTEM,         // Pool type
            WINBIO_FLAG_DEFAULT,        // Configuration and access
            NULL,                       // Array of biometric unit IDs
            0,                          // Count of biometric unit IDs
            NULL,                       // Database ID
            &sessionHandle              // [out] Session handle
    if (FAILED(hr))
        wprintf_s(L"\n WinBioOpenSession failed. hr = 0x%x\n", hr);
        goto e_Exit;

    wprintf_s(L"\n Calling WinBioLocateSensorWithCallback.");
    hr = WinBioLocateSensorWithCallback(
                sessionHandle,          // Open biometric session
                LocateSensorCallback,   // Callback function
                NULL                    // Optional context
    if (FAILED(hr))
        wprintf_s(L"\n WinBioLocateSensorWithCallback failed.");
        wprintf_s(L"hr = 0x%x\n", hr);
        goto e_Exit;
    wprintf_s(L"\n Swipe the sensor ...\n");

    // Cancel the identification if the bCancel flag is set.
    if (bCancel)
        wprintf_s(L"\n Starting CANCEL timer...\n");
        Sleep( 7000 );

        wprintf_s(L"\n Calling WinBioCancel\n");
        hr = WinBioCancel( sessionHandle );
        if (FAILED(hr))
            wprintf_s(L"\n WinBioCancel failed. hr = 0x%x\n", hr);
            goto e_Exit;

    // Wait for the asynchronous identification process to complete 
    // or be canceled.
    hr = WinBioWait( sessionHandle );
    if (FAILED(hr))
        wprintf_s(L"\n WinBioWait failed. hr = 0x%x\n", hr);


    if (sessionHandle != NULL)
       wprintf_s(L"\n Closing the session.\n");

        hr = WinBioCloseSession(sessionHandle);
        if (FAILED(hr))
            wprintf_s(L"\n WinBioCloseSession failed. hr = 0x%x\n", hr);
        sessionHandle = NULL;

    wprintf_s(L"\n Hit any key to exit...");

    return hr;

// The following function is the callback for 
// WinBioLocateSensorWithCallback. The function filters the response 
// from the biometric subsystem and writes a result to the console window.
VOID CALLBACK LocateSensorCallback(
    __in_opt PVOID LocateCallbackContext,
    __in HRESULT OperationStatus,
    __in WINBIO_UNIT_ID UnitId

    wprintf_s(L"\n LocateSensorCallback executing.");

    // A sensor could not be located.
    if (FAILED(OperationStatus))
        wprintf_s(L"\n LocateSensorCallback failed.");
        wprintf_s(L"OperationStatus = 0x%x\n", OperationStatus);
    // A sensor was located.
        wprintf_s(L"\n Selected unit ID: %d\n", UnitId);


Minimum supported client

Windows 7 [desktop apps only]

Minimum supported server

Windows Server 2008 R2 [desktop apps only]