AddressOf, .NET, and VB6.0 interoperability

[BoloBaby]

OK, here's the problem...

I have a digital input/output card that exposes IRQs (digital input
change-of-state) through a DLL function.

In VB6.0, I can use this ability through code that looks like this:

[Class1]

Public sub test()
DIO_INT1_EventMessage 0, 0, 0, 0, AddressOf BE_ReadPort
end sub

[standard module]

Declare Function DIO_INT1_EventMessage Lib "Pci-Dask.dll" (ByVal CardNumber
As Integer, ByVal Int1Mode As Integer, ByVal windowHandle As Long, ByVal
message As Long, ByVal callbackAddr As Long) As Integer

Public sub BE_ReadPort()
'do some stuff
end sub

Take note that the sub that handles the event HAS to be in the standard
module and NOT in a class module. This is just a limitation of VB6.0. This
means that I can't raise any events in that sub... which is what I *really*
need to do.

Anyway, the inability to raise events led me to try and set up a PInvoke
wrapper in .NET. The problem is, the VB6.0 DLL for the digital I/O card
accepts only "ByVal callbackAddr As Long" as the address for the callback
function. In .NET, the AddressOf operator returns a System.Delegate type.

How can I make this code point to my delegate function in .NET? Or,
alternatively, how can I use VB6.0 to raise the event? I already tried
using a global object to raise the events. Doesn't seem to work...

Thanks.

 

[Konrad L. M. Rudolph]

Two answers:

Take note that the sub that handles the event HAS to be in the standard
module and NOT in a class module. This is just a limitation of VB6.0. This
means that I can't raise any events in that sub... which is what I *really*
need to do.

why don't you just invoke the class and let it handle the event? Just
declare an object of the class on module scope. In the class, before
calling the API, you set this object instance to "Me". then you can call
a public procedure of this class from the callback function. Now, back
in the class this certain public procedure uses RaiseEvent to raise an
event.
It's as simple as this.

Anyway, the inability to raise events led me to try and set up a PInvoke
wrapper in .NET. The problem is, the VB6.0 DLL for the digital I/O card
accepts only "ByVal callbackAddr As Long" as the address for the callback
function. In .NET, the AddressOf operator returns a System.Delegate type.

No problem at all, just declare the API accordingly, use the delegate
type. The framework will take care of the needed conversion.

Example:

\\
Public Delegate Function FontEnumProc( _
ByVal NLF As LOGFONT, _
ByVal NTM As TEXTMETRIC, _
ByVal FontType As Int32, _
ByVal LParam As Int32 _
) As Int32

Public Declare Function EnumFontFamilies Lib "gdi32" Alias
"EnumFontFamiliesA" ( _
ByVal hDC As Int32, _
ByVal lpszFamily As String, _
ByVal lpEnumFontFamProc As FontEnumProc, _
ByVal lParam As Int32 _
) As Long
///

should work just as well with your API.

 

[Herfried K. Wagner [MVP]]

No problem at all, just declare the API accordingly, use the delegate
type. The framework will take care of the needed conversion.


Example:

\\
Public Delegate Function FontEnumProc( _
ByVal NLF As LOGFONT, _
ByVal NTM As TEXTMETRIC, _
ByVal FontType As Int32, _
ByVal LParam As Int32 _
) As Int32

Public Declare Function EnumFontFamilies Lib "gdi32" Alias
"EnumFontFamiliesA" ( _

ByVal hDC As Int32, _
ByVal lpszFamily As String, _
ByVal lpEnumFontFamProc As FontEnumProc, _
ByVal lParam As Int32 _
) As Long
///

should work just as well with your API.

ACK, but don't forget to store a reference to the delegate you pass to
the API function in order to prevent the GC from removing it.

 

[Tom Shelton]

OK, here's the problem...

I have a digital input/output card that exposes IRQs (digital input
change-of-state) through a DLL function.

In VB6.0, I can use this ability through code that looks like this:

[Class1]

Public sub test()
DIO_INT1_EventMessage 0, 0, 0, 0, AddressOf BE_ReadPort
end sub

[standard module]

Declare Function DIO_INT1_EventMessage Lib "Pci-Dask.dll" (ByVal CardNumber
As Integer, ByVal Int1Mode As Integer, ByVal windowHandle As Long, ByVal
message As Long, ByVal callbackAddr As Long) As Integer

Declare Function DIO_INT1_EventMessage Lib "Pci-Dask.dll" _
(ByVal CardNumber As Short, _
ByVal Init1Mode As Short, _
ByVal windowHandle As IntPtr, _
ByVal message As Integer, _
ByVal callbackAddr As MethodInvoker) As Short

Private mi As MethodInvoker = New MethodInvoker(BE_ReadPort)

Private Sub CallIt()
DIO_INT1_EventMessage(..., ..., ..., Me.Handle, ..., mi)
End Sub

Private sub BE_ReadPort()
'do some stuff
end sub

Something like the above should get you up and running