Help, Calling c++ dll from vb.net

[xin.huang.xh@gmail.com]

Hi All:

Please help me out here. I try to call a C++ dll from my VB.NET code.
I follow the examples given on the web, but it does not work for
me!!! It drives me crazy, so please help me out. Here is what I did


Create an empty VC++ dll project from Visual Studio 2003. Create a
test.cpp file and add the following


long _stdcall test(long a) {
return a;



}


Create a test.def file and add the following

LIBRARY "test"


EXPORTS
test


Create a VB windows application. Here is what is given in the file


Public Class Form1
Inherits System.Windows. Forms.Form
Private Declare Function test Lib "location of the dll in my
computer" (ByVal b As Long) as Long


Private Sub Button1_Click( ..... ) Handles Button1.Click
MsgBox(test(100 0))
End Sub


End Class


When I click the button, it returns a number that is very large (so
it
is NOT 1000).


I also try the same thing in VS2005 on another machine in my lab.
This time I get an error


PInvokeStackImb alance was detected


I just don't know what is going on. It just a very simple example and
just cannot get it work.


So, any suggestions will be much appreciated,


Thanks alot


Xin

[Stanimir Stoyanov]

Re: Help, Calling c++ dll from vb.net

<xin.huang.xh@g mail.comwrote in message
news:1188569508 .477279.194980@ w3g2000hsg.goog legroups.com...

Please help me out here. I try to call a C++ dll from my VB.NET code.
I follow the examples given on the web, but it does not work for
me!!!

Hello Xin,

You have to specify "C" linkage as your DLL is currently export C++-style
functions whose names are mangled.

See http://msdn2.microsoft.com/en-us/library/ms857730.aspx.

Best Regards,
Stanimir Stoyanov
www.stoyanoff.info | www.aeroxp.org

[=?Utf-8?B?cm1hY2lhcw==?=]

RE: Help, Calling c++ dll from vb.net

In .NET, the size of a long is 8 bytes. I'm guessing that the architecture
for your machine a long in C++ is 4 bytes. That would cause a stack
imbalance. Try changing your .NET declartion to an Integer instead of a long.

In addition, you can always try playing around with the DllImport Attribute
instead:

Imports System.Runtime. InteropServices

Public Class Form1

<DllImport("C:\ MyDll.dll",
CallingConventi on:=CallingConv ention.StdCall) _
Private Shared Function Test(<MarshalAs (UnmanagedType. I4)ByVal b As
Integer) As Integer
End Function


End Class

"xin.huang.xh@g mail.com" wrote:

Hi All:
>
Please help me out here. I try to call a C++ dll from my VB.NET code.
I follow the examples given on the web, but it does not work for
me!!! It drives me crazy, so please help me out. Here is what I did
>
>
Create an empty VC++ dll project from Visual Studio 2003. Create a
test.cpp file and add the following
>
>
long _stdcall test(long a) {
return a;
>
>
>
}
>
>
Create a test.def file and add the following
>
LIBRARY "test"
>
>
EXPORTS
test
>
>
Create a VB windows application. Here is what is given in the file
>
>
Public Class Form1
Inherits System.Windows. Forms.Form
Private Declare Function test Lib "location of the dll in my
computer" (ByVal b As Long) as Long
>
>
Private Sub Button1_Click( ..... ) Handles Button1.Click
MsgBox(test(100 0))
End Sub
>
>
End Class
>
>
When I click the button, it returns a number that is very large (so
it
is NOT 1000).
>
>
I also try the same thing in VS2005 on another machine in my lab.
This time I get an error
>
>
PInvokeStackImb alance was detected
>
>
I just don't know what is going on. It just a very simple example and
just cannot get it work.
>
>
So, any suggestions will be much appreciated,
>
>
Thanks alot
>
>
Xin
>
>

[xin.huang.xh@gmail.com]

Re: Help, Calling c++ dll from vb.net

On Aug 31, 11:28 am, rmacias <rmac...@newsgr oup.nospamwrote :

In .NET, the size of a long is 8 bytes. I'm guessing that the architecture
for your machine a long in C++ is 4 bytes. That would cause a stack
imbalance. Try changing your .NET declartion to an Integer instead of a long.
>
In addition, you can always try playing around with the DllImport Attribute
instead:
>
Imports System.Runtime. InteropServices
>
Public Class Form1
>
<DllImport("C:\ MyDll.dll",
CallingConventi on:=CallingConv ention.StdCall) _
Private Shared Function Test(<MarshalAs (UnmanagedType. I4)ByVal b As
Integer) As Integer
End Function
>
End Class
>
>
>
"xin.huang...@g mail.com" wrote:

Hi All:

>

Please help me out here. I try to call a C++ dll from my VB.NET code.
I follow the examples given on the web, but it does not work for
me!!! It drives me crazy, so please help me out. Here is what I did

>

Create an empty VC++ dll project from Visual Studio 2003. Create a
test.cpp file and add the following

>

long _stdcall test(long a) {
return a;

>

}

>

Create a test.def file and add the following

>

LIBRARY "test"

>

EXPORTS
test

>

Create a VB windows application. Here is what is given in the file

>

Public Class Form1
Inherits System.Windows. Forms.Form
Private Declare Function test Lib "location of the dll in my
computer" (ByVal b As Long) as Long

>

Private Sub Button1_Click( ..... ) Handles Button1.Click
MsgBox(test(100 0))
End Sub

>

End Class

>

When I click the button, it returns a number that is very large (so
it
is NOT 1000).

>

I also try the same thing in VS2005 on another machine in my lab.
This time I get an error

>

PInvokeStackImb alance was detected

>

I just don't know what is going on. It just a very simple example and
just cannot get it work.

>

So, any suggestions will be much appreciated,

>

Thanks alot

>

Xin- Hide quoted text -

>
- Show quoted text -

Hi Stanimir and rmacias

Thank you very much for your suggestions. I incoporate both
suggestions and use the DllImport. It works NOW. :D

Xin

[Phoenix]

Re: Help, Calling c++ dll from vb.net

On Aug 31, 8:28 pm, rmacias <rmac...@newsgr oup.nospamwrote :

In .NET, the size of a long is 8 bytes. I'm guessing that the architecture
for your machine a long in C++ is 4 bytes. That would cause a stack
imbalance. Try changing your .NET declartion to an Integer instead of a long.
>
In addition, you can always try playing around with the DllImport Attribute
instead:
>
Imports System.Runtime. InteropServices
>
Public Class Form1
>
<DllImport("C:\ MyDll.dll",
CallingConventi on:=CallingConv ention.StdCall) _
Private Shared Function Test(<MarshalAs (UnmanagedType. I4)ByVal b As
Integer) As Integer
End Function
>
End Class
>
"xin.huang...@g mail.com" wrote:

Hi All:

>

Please help me out here. I try to call a C++ dll from my VB.NET code.
I follow the examples given on the web, but it does not work for
me!!! It drives me crazy, so please help me out. Here is what I did

>

Create an empty VC++ dll project from Visual Studio 2003. Create a
test.cpp file and add the following

>

long _stdcall test(long a) {
return a;

>

}

>

Create a test.def file and add the following

>

LIBRARY "test"

>

EXPORTS
test

>

Create a VB windows application. Here is what is given in the file

>

Public Class Form1
Inherits System.Windows. Forms.Form
Private Declare Function test Lib "location of the dll in my
computer" (ByVal b As Long) as Long

>

Private Sub Button1_Click( ..... ) Handles Button1.Click
MsgBox(test(100 0))
End Sub

>

End Class

>

When I click the button, it returns a number that is very large (so
it
is NOT 1000).

>

I also try the same thing in VS2005 on another machine in my lab.
This time I get an error

>

PInvokeStackImb alance was detected

>

I just don't know what is going on. It just a very simple example and
just cannot get it work.

>

So, any suggestions will be much appreciated,

>

Thanks alot

>

Xin

Hi Friend ,

Could you please have a look at following :

http://groups.google.co.in/group/microsoft.public.dotnet.languages.vb/browse_thread/thread/d5c4ee1c925fa303/b7cadcdcc47ac223?hl=en#b7cadcdcc47ac223

Any suggestions would be highly appreciated :)

Sincerely,
Sudhansu