ERROR: Object Reference Not Set to an Instance of an Object

[Michael Chong]

I have an (exe) executable program created in VB.NET 2003 that calls to a
MFC DLL written in VC++.NET 2003. I always get an error msg
"NullReferenceE xception: Object Reference Not Set to an Instance of an
Object" when my exe calls the following codes:

in VB.NET

Declare Function test Lib "C:\Cyob\IOComm \Debug\IOComm.d ll" _
(ByVal a As Long, ByRef b As Integer) As Integer

Dim did As Integer
Dim ret As Integer

ret = test(PortHnd, did) //ERROR: Object Reference Not Set to an
Instance of an Object


in VC++.NET

extern "C" int APIENTRY test(HANDLE a, int *b)
{
*b=55; //ERROR: Object Reference Not Set to an Instance of an
Object
return 99;
}


Why is this happening? Any idea in solving such matter?
Thanks in Advance

Michael.

[Herfried K. Wagner [MVP]]

Re: ERROR: Object Reference Not Set to an Instance of an Object

* "Michael Chong" <michael@cyob.c om.my> scripsit:[color=blue]
> I have an (exe) executable program created in VB.NET 2003 that calls to a
> MFC DLL written in VC++.NET 2003. I always get an error msg
> "NullReferenceE xception: Object Reference Not Set to an Instance of an
> Object" when my exe calls the following codes:
>
> in VB.NET
>
> Declare Function test Lib "C:\Cyob\IOComm \Debug\IOComm.d ll" _
> (ByVal a As Long, ByRef b As Integer) As Integer[/color]

'Long' -> 'IntPtr'.

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://dotnet.mvps.org/dotnet/faqs/>