LPSTR -> String : Type Incompatibility Issue

[Michael Chong]

Another same issue on "NullReferenceE xception" :-
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 String) 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, LPSTR b)
{
strcpy(b, "hello"); //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.

[Michael Chong]

Sorry, the "Dim did as Integer" should be "Dim did as String"
I believe is DataType issue from VC++.NET (LPSTR) pass to VB.NET (String)

When I try to replace String with IntPtr, it doesn't give me error but the
return value for "did variable" is some numbers.
Plz help! TQ


"Michael Chong" <mi*****@cyob.c om.my> wrote in message
news:Og******** ******@tk2msftn gp13.phx.gbl...

Another same issue on "NullReferenceE xception" :-
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 String) 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, LPSTR b)
{
strcpy(b, "hello"); //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.

[Wild Wind]

> "Michael Chong" <mi*****@cyob.c om.my> wrote in message

news:Og******** ******@tk2msftn gp13.phx.gbl...

Another same issue on "NullReferenceE xception" :-
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 String) 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, LPSTR b)
{
strcpy(b, "hello"); //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.

Michael,

It looks like you haven't allocated memory to copy the
"hello" to in your strcpy call.

Try putting

b = new CHAR[strlen("hello") + 1];

before your call to strcpy.

--
Akin

aknak at aksoto dot idps dot co dot uk