Visual Basic.NET

Create Callback Routine

Create Callback Function

The callback function has the following format. You can specify any name for this function.

Protected Sub CallBackProc(ByVal Id As Short, ByVal Message As Short, ByVal wParam As Integer, ByVal lParam As Integer, ByVal Param As IntPtr)

Use Delegate

In Visual Basic, please use delegate to handle a function pointer.
The delegate declarations for each callback routine are written in the CAIO.vb file.

Analog Input	PAICALLBACK
Analog Output	PAOCALLBACK
Counter	PCNTCALLBACK
Timer	PTMCALLBACK

Register Callback Function

Please use the following functions to register callback functions.

Analog Input	AioSetAiCallBackProc
Analog Output	AioSetAoCallBackProc
Counter	AioSetCntCallBackProc
Timer	AioSetTmCallBackProc

Flow of Registering Callback Function

. Initialize delegate
. Get the GCHandle to prevent the garbage collector from moving the delegate used for interrupt processing
. Get a stable pointer to the delegate used for interrupt processing
. Register the retrieved stable pointer by using functions such as AioSetAiCallBackProc function
. Release the GCHandle for the delegate used for interrupt processing, when it become unnecessary (for example, when the application terminates)

For these specific coding content, please refer to samples and Note of Using Visual Basic .NET.