Access Violation Exception was unhandled when calling a DLL VB .NET 2008

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VB

Hello,

I need to write-read from a program to a RFID USB Card Writer.

The Card Writer is deliverd with a DLL 32 bit which has certain function.

When trying to call funtions from the DLL there is always a error coming up 'Access Violation Exception was unhandled when calling a DLL'

I am not familiar with dll's so does anyone has a idea.

Maybe the DLL is not working for .net 2008 there are examples deliverd for VB6 an VC but not for .net. The supplier of the RFID reader has not specified that it wont work with win7 but since i got errors.

I have taken a windows 7 and installed a old VB6 on it (there where errors when installing that VB6 is is not compatible with win7) but the installation is working.

So i have used the example on this machine in VB6 and there the reader is responding and gives no error.


I use this on Windows 7 32 bit version.

Can anyone give me some advise please

VB6 Code that is working

hexkey = "ffffffffffff"
st = dc_load_key_hex(ByVal icdev, 0, 1, ByVal hexkey)  'Load Key of Sector 1 to the Reader,correspond to the following authentication
If st <> 0 Then
      List1.AddItem ("dc_Load_key_hex Error!")
      Exit Sub
End If
List1.AddItem ("dc_Load_key_hex OK!")

VB .Net 2008 Code with the access Violation Exception

hexkey = "ffffffffffff"

        st = dc_load_key_hex(icdev, 0, 1, hexkey)  'Load Key of Sector 1 to the Reader,correspond to the following authentication
        If st <> 0 Then
            TextBox1.Text = "dc_Load_key_hex Error!"
            Exit Sub
        End If
        TextBox1.Text = "dc_Load_key_hex OK!"

Anyone with a good hint ?

I am wondering if the DLL might be not compatible with .net ? can this be the problem ?

Thanks.

Didier