Need to wrap a dll so it can be used in VB.Net

Jonathan Trahair

14y5.7k

Hi. I have a commercial dll which is invisible to VB.net, ie. I can't use it. I think I need to put it in a wrapper.

Are there some dlls that can't be wrapped? What do I need to know about the dll to determine whether it can be wrapped?

I'm OK in VB.net, but no knowledge of VC++, C# etc.

I've seen tutorials, but they refer to a dll which a) can be wrapped, and b) about which you know everything. I have some documentation as to calls etc., but nothing more.

Thank you.

More info: the dll is to do with waking up a battery-operated Bluetooth printer that has fallen asleep to conserve battery charge. The printer is 'connected' to a battery operated handheld Windows CE terminal, like parcel delivery drivers have. The dll is an Atinav product, and they have gone bust, I think. Allegedly.

4 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes14y ago
Accepted answer
Yes, that looks like a C dll which I assume is called albtradio.dll.

I'd place the dll in your application folder and the add this class to your project:

Imports System.Runtime.InteropServices ' Needed for DllImport attribute

Public Class Albtradio

_
Public Shared Function BTRadioOn() As Boolean
End Function

_
Public Shared Function BTRadioOff() As Boolean
End Function

_
Public Shared Function BTRadioStatus(ByRef status As UInteger) As Boolean
End Function

End Class

You should then be able to call the functions from some other class, like this:

Dim bOn As Boolean = Albtradio.BTRadioOn() ' if bOn is true it worked

Dim bOff As Boolean = Albtradio.BTRadioOff() ' if bOff is true it worked

Dim status As UInteger
Dim bStatus As Boolean = Albtradio.BTRadioStatus(status) ' if bStatus is true it worked
If status = 0 Then Console.WriteLine("Status is Power-down")

0
Sam Hobbs14y ago
To be sure that the DLL is a regular DLL, I would look in the albtradio.h file, but I am not sure how to describe what to look for.

The fact that it does not work when you try to add a reference using the DLL does not prove that the DLL is a regular DLL. It is possible for a type library to exist in a separate file. Note that the terminology can be confusing; the terms that I think are more useful are "regular DLL" and "COM object". For example, note that Vulpes says "if the dll is written in C (as low level stuff often is) or it's a C++/VB6 COM dll" and "that looks like a C dll". I think he intends to mean that the DLL is a regular DLL, yet "VB6 COM dll" is not a regular DLL. A VB 6 DLL cannot be called using "Platform Invoke mechanism (DllImport attribute or the older Declare statement)." Vulpes is differentiating between a regular DLL and a COM DLL by calling them a C DLL and a C++ DLL respectively but it is possible to write a COM DLL using C and a regular DLL using C++.

To get an idea of what makes a COM object is, look at my Introduction to COM Automation. Note that in that I use the term COM Automation but that is essentially the same as COM Object. I admit that that article is not easy to understand, but I hope it at least gives an idea of the difference between a regular DLL and a DLL that can be used as a COM object.
0
Jonathan Trahair14y ago
Here's what I know: in VB, Add References, Browse, choose the dll, error message reads:
A reference to 'C:\whatever.dll' could not be added. Please make sure that the file is accessible, and that it is a valid assembly or COM component.

I have this much documentation - see below.

Does this tell me if it's a C or COM dll?

Thank you for your reply.

//Document starts:
This document describes the APIs provided for Power –UP/Power-Down Built-in Bluetooth module of JettXL devices from Two tech.

Inorder to program Bluetooth using avelinkBT SDK, you must power-up the built-in module before calling any of the Bluetooth APIs.Similarly you must power-down the Bluetooth once the work is over.

1)     BOOLEAN BTRadioOn()

This method is used to power-up the Built-in Bluetooth module in JettXL Devices.

Parameters : NIL

Returns     : Boolean, TRUE if success ; FALSE if failure



2)     BOOLEAN BTRadioOff()

This method is used to power-down the Built-in Bluetooth module in JettXL Devices.

Parameters : NIL

Returns     : Boolean, TRUE if success ; FALSE if failure

3)     BOOLEAN BTRadioStatus(DWORD *status);

This method is used to get the current power status of the Builtin Bluetooth module JettXL Devices.

Parameters :

Status       : [in/out] Retreives the current power state. A value 0 indicates the power-down.

Returns     : Boolean, TRUE if success ; FALSE if failure

Requirements
          Header: include albtradio.h
          Library: albtradio.lib

//Document ends.
0
Vulpes14y ago
Broadly, if the dll is written in C (as low level stuff often is) or it's a C++/VB6 COM dll, then it will be usable from VB.NET. Otherwise it won't be.

In particular Java ME code isn't usable from VB.NET though this is usually easy to spot from the 'import' statements in the examples.

If you're sure it's not Java and the examples you have are simply calling functions and there's no sign of any objects or interfaces, then it's probably a C dll. In that case you should be able to call the functions using the Platform Invoke mechanism (DllImport attribute or the older Declare statement).

If it's a COM dll (you can usually tell from the proliferation of interfaces), then you should be able to do something using COM interop.
0