WinBioLockUnit function

Locks a biometric unit for exclusive use by a single session. Starting with Windows 10, build 1607, this function is available to use with a mobile image.


  _In_ WINBIO_UNIT_ID        UnitId


SessionHandle [in]

A WINBIO_SESSION_HANDLE value that identifies an open biometric session. Open a synchronous session handle by calling WinBioOpenSession. Open an asynchronous session handle by calling WinBioAsyncOpenSession.

UnitId [in]

A WINBIO_UNIT_ID value that specifies the biometric unit to be locked.

Return value

If the function succeeds, it returns S_OK. If the function fails, it returns an HRESULT value that indicates the error. Possible values include, but are not limited to, those in the following table. For a list of common error codes, see Common HRESULT Values.

Return codeDescription

The session handle is not valid.


The UnitId parameter cannot contain zero.


The operation could not be completed because the specified biometric unit is currently being used for an enrollment transaction (system pool only).


The biometric unit cannot be locked because the specified session already has another unit locked.



If the specified biometric unit is locked by another session, WinBioLockUnit will block the calling thread until the session that owns the biometric unit releases its lock.

Call the WinBioUnlockUnit function to cancel any pending lock request and release all locks held by the session.

To use WinBioLockUnit synchronously, call the function with a session handle created by calling WinBioOpenSession. The function blocks until the operation completes or an error is encountered.

To use WinBioLockUnit asynchronously, call the function with a session handle created by calling WinBioAsyncOpenSession. The framework allocates a WINBIO_ASYNC_RESULT structure and uses it to return information about operation success or failure. The WINBIO_ASYNC_RESULT structure is returned to the application callback or to the application message queue, depending on the value you set in the NotificationMethod parameter of the WinBioAsyncOpenSession function:

  • If you choose to receive completion notices by using a callback, you must implement a PWINBIO_ASYNC_COMPLETION_CALLBACK function and set the NotificationMethod parameter to WINBIO_ASYNC_NOTIFY_CALLBACK.
  • If you choose to receive completion notices by using the application message queue, you must set the NotificationMethod parameter to WINBIO_ASYNC_NOTIFY_MESSAGE. The framework returns a WINBIO_ASYNC_RESULT pointer to the LPARAM field of the window message.

To prevent memory leaks, you must call WinBioFree to release the WINBIO_ASYNC_RESULT structure after you have finished using it.


The following function calls WinBioLockUnit to lock the biometric unit before calling WinBioIdentify to identify the user. Link to the Winbio.lib static library and include the following header files:

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

HRESULT LockUnlock( )
    // Declare variables.
    HRESULT hr = S_OK;
    WINBIO_IDENTITY identity = {0};
    WINBIO_UNIT_ID unitId = 0;
    WINBIO_REJECT_DETAIL rejectDetail = 0;
    BOOL lockAcquired = FALSE;

    // 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 WinBioEnumBiometricUnits failed. hr = 0x%x\n", hr);
        goto e_Exit;

    // Lock the session. The Biometric unit ID (1) is hard coded in
    // this example.
    hr = WinBioLockUnit( sessionHandle, 1 );
    if (FAILED(hr))
        wprintf_s(L"\n WinBioLockUnit failed. hr = 0x%x\n", hr);
        goto e_Exit;
    wprintf_s(L"\n Biometric unit #1 is locked.\n");
    lockAcquired = TRUE;

    // Locate the biometric sensor and retrieve a WINBIO_IDENTITY object.
    // You must swipe your finger on the sensor.
    wprintf_s(L"\n Calling WinBioIdentify - Swipe finger on sensor...\n");
    hr = WinBioIdentify( 
    wprintf_s(L"\n Swipe processed - Unit ID: %d\n", unitId);
    if (FAILED(hr))
        wprintf_s(L"\n WinBioIdentify failed. hr = 0x%x\n", hr);
        goto e_Exit;


    // Unlock the biometric unit if it is locked.
    if (lockAcquired == TRUE)
        hr = WinBioUnlockUnit( sessionHandle, 1 );
        if (FAILED(hr))
            wprintf_s(L"\n WinBioUnlockUnit failed. hr = 0x%x\n", hr);
        wprintf_s(L"\n Biometric unit #1 is unlocked.\n");
        lockAcquired = FALSE;

    if (sessionHandle != NULL)
        sessionHandle = NULL;

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

    return hr;


Minimum supported client

Windows 7 [desktop apps only]

Minimum supported server

Windows Server 2008 R2 [desktop apps only]


Winbio.h (include Winbio.h)





See also