AddressOf from VB6 to .Net VB

22 Mar 2006 10:05 AM

pavel.orehov@gmail.com

Private Delegate Function WndCallback _
        (ByVal hw As Integer, _
        ByVal uMsg As Integer, _
        ByVal wParam As Integer, _
        ByVal lParam As Integer) As Integer

Private Declare Function SetWindowLong Lib "USER32.DLL" Alias
"SetWindowLongA" _
        (ByVal hwnd As Integer, _
        ByVal nIndex As Integer, _
        ByVal dwNewLong As WndCallback) As WndCallback

Private PrevWndPRoc As WndCallback

Public Sub RegisterFormForOrientationDetection(ByRef f As
System.Windows.Forms.Form)
        PrevWndPRoc = SetWindowLong(f.Handle.ToInt32(), _
                                    GWL_WNDPROC, _
BBB->                           AddressOf WndProcWithRotationDetection)
End Sub

Hi,

I have converted the VB6 code to .NET according to microsoft.
The compilation is okey, but i get an exception in runtime on line BBB
that says:

Invalid function pointer 0xffff0557 was passed into the runtime to be
converted to a delegate. Passing in invalid function pointers to be
converted to delegates can cause crashes, corruption or data loss.

What i did wrong ?

Thanks,
Pavel.

22 Mar 2006 10:11 AM

pavel.orehov@gmail.com

Sorry, i forgit the function itself.

Public Function WndProcWithRotationDetection(ByVal hw As Integer, _
                                          ByVal uMsg As Integer, _
                                          ByVal wParam As Integer, _
                                          ByVal lParam As Integer) As
Integer
          ' Do the job

End Functon

22 Mar 2006 11:05 AM

José_Manuel_Agüero

Hello Pavel,

If your WndProcWithRotationDetection function is not in a module, you must declare it Shared.
With Windows API functions that admit ANSI and Unicode versions, you should declare them Auto to avoid trouble when passing strings (it's only my opinion):
Declare Auto Function SetWindowLong Lib "USER32.DLL" (ByVal hwnd ...

Anyway, if you are processing Windows messages sent to your form, you don't need to do Platform Invoke: You can override the functions PreProcessMessage and WndProc.
If you only want to send messages, you can override DefWndProc.
You can also create a class that implements IMessageFilter and use Application.AddMessageFilter to activate it. This only let you see the messages and to stop them from reaching WndProc.

Regards.

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22 Mar 2006 9:33 PM

Mattias Sjögren

Check out the NativeWindow class for a better way to do window
subclassing in maanged code.

Mattias

--
Mattias Sjögren [C# MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
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