WinBioAsyncEnumBiometricUnits function (winbio.h)

Article
10/13/2021

Asynchronously enumerates all attached biometric units that match the input factor type. For a synchronous version of this function, see WinBioEnumBiometricUnits. Starting with Windows 10, build 1607, this function is available to use with a mobile image.

Syntax

HRESULT WinBioAsyncEnumBiometricUnits(
  [in] WINBIO_FRAMEWORK_HANDLE FrameworkHandle,
  [in] WINBIO_BIOMETRIC_TYPE   Factor
);

Parameters

[in] FrameworkHandle

Handle to the framework session opened by calling WinBioAsyncOpenFramework.

[in] Factor

A bitmask of WINBIO_BIOMETRIC_TYPE flags that specifies the biometric unit types to be enumerated. Only WINBIO_TYPE_FINGERPRINT is currently supported.

Return value

The function returns an HRESULT indicating success or failure. Note that success indicates only that the arguments were valid. Failures encountered during the execution of the operation will be returned asynchronously to a WINBIO_ASYNC_RESULT structure using the notification method specified in the call to WinBioAsyncOpenFramework.

Return code	Description
E_HANDLE	You must set the FrameworkHandle argument.
E_INVALIDARG	The bitmask contained in the Factor parameter contains one or more an invalid type bits.
E_OUTOFMEMORY	There was insufficient memory to complete the request.
WINBIO_E_DISABLED	Current administrative policy prohibits use of the Windows Biometric Framework API.
WINBIO_E_INCORRECT_SESSION_TYPE	The FrameworkHandle argument must represent an asynchronous framework session.
WINBIO_E_SESSION_HANDLE_CLOSED	The session handle has been marked for closure.

Remarks

The WinBioAsyncEnumBiometricUnits function uses a handle to the framework session opened by calling WinBioAsyncOpenFramework. The framework allocates a WINBIO_ASYNC_RESULT structure and uses it to return information about operation success or failure. If the enumeration operation is successful, the framework returns an array of schemas that include information about each enumerated biometric unit. If the operation is unsuccessful, the framework uses the WINBIO_ASYNC_RESULT structure to return error information. The 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 WinBioAsyncOpenFramework 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.

The array of schemas is returned in an EnumBiometricUnits structure nested inside the WINBIO_ASYNC_RESULT structure. You must call WinBioFree to release the WINBIO_ASYNC_RESULT structure after you have finished using it.

Calling WinBioAsyncEnumBiometricUnits causes a single notification to be sent to the client application.

Requirements

Requirement	Value
Minimum supported client	Windows 8 [desktop apps only]
Minimum supported server	Windows Server 2012 [desktop apps only]
Target Platform	Windows
Header	winbio.h (include Winbio.h)
Library	Winbio.lib
DLL	Winbio.dll