Adapting a DLL to VB.NET, using PINVOKE

Hrizip

I am trying to dissasemble a .net dll via reflector, one that has been in use in our company for ages, as practice. My future task will be to produce similar dll-a that are com interoparabile and activex compliant. I am doing this in VB.net, and I have already been told that this is a big no-no, dlls of this sort are supposed to be made with C++ people say. I would guess that they are stating this because C++ uses pointers (which are heavily used in many DLLs when it comes to pointing to a pointer - i.e. memory location that holds particular relevant info). Be as it may, I wish to proceed building this dll in vb.net to see how far I can get before I am forced to switch to C++ or C#... I have already made a lot of fixes to the code, thus reducing the number of errors from over 120 to 30 which is, I would guess, a good start, but now I am facing several errors that are above my level of knowledge (I am a beginner after all) and I would like to get some information from people who are more experienced than me. * First problem I encountered is the following: (this is an excerpt of code dealing with events that happen on a SERIAL port).

Public Custom Event OnCTS As OnCTS
AddHandler(ByVal value As OnCTS)
Me.OnCTS = DirectCast(Delegate.Combine(DirectCast(Me.OnCTS, Delegate), DirectCast(value, Delegate)), OnCTS)
End AddHandler
RemoveHandler(ByVal value As OnCTS)
Me.OnCTS = DirectCast(Delegate.Remove(DirectCast(Me.OnCTS, Delegate), DirectCast(value, Delegate)), OnCTS)
End RemoveHandler
End Event

This is what the reflector did for me, unfortunately the first "DELEGATE" keyword after DirectCast has an error attached to it: "expression expected". I have tried using "raiseevent" instead but if I use that, another piece of code later will not work. Currently I have this:

Public Custom Event OnCTS As OnCTS
AddHandler(ByVal value As OnCTS)

        End AddHandler

        RaiseEvent()

        End RaiseEvent

        RemoveHandler()

        End RemoveHandler
    End Event

But I do not know the proper syntax for this nor where to begin. I have only recently started doing event driven code. * A similar error (DELEGATE keyword, "keyword does not name a type") happens in this line of code:

Me.parent.Invoke(DirectCast(New EventHandler(AddressOf callback.ToMainThread), Delegate))

* The third problem is in this line of code

Luc Pattyn

Hi, I will attempt and answer a couple of your issues in separate messages, so they can expand individually if required. try this:

Public Enum VasKeys as uint32
ClassesRoot = &H80000000U
CurrentUser = &H80000001U
LocalMachine = &H80000002U
Users = &H80000003U
End Enum

there are a couple of suffixes that indicate a different type, U means unsigned. it is documented here[^]. :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

Prolific encyclopedia fixture proof-reader browser patron addict?
We all depend on the beast below.

Luc Pattyn

the prototype should indicate either an array or a pointer, so try this:

_
Private Shared Function WriteFile(ByVal handle As IntPtr, ByRef bytes As Byte(), ByVal numBytesToWrite As Integer, ByRef numBytesWritten As Integer, ByRef overlapped As OVERLAPPED) As Integer
End Function

I made bytes an array of bytes, not a single byte. I expect that to work for you, I haven't done it in VB.NET yet, I normally do C# (and P/Invoke from C# to C). :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

Prolific encyclopedia fixture proof-reader browser patron addict?
We all depend on the beast below.

Luc Pattyn

you are mixing signed and unsigned integers. It isn't very important which you choose, however being consistent is what matters. So either make BR an unsigned integer (use the U suffix again!), or modify the structure to a signed baudrate. The P/Invoke stuff will not mind you doing so. :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

Prolific encyclopedia fixture proof-reader browser patron addict?
We all depend on the beast below.

Luc Pattyn

Hrizip wrote:

Dim key As New RegKey(&H80000002)

I don't know what class RegKey is, nor what constructor(s) it has. If it needs an unsigned integer parameter, once again apply a U suffix or switch to a signed integer definition. :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

Prolific encyclopedia fixture proof-reader browser patron addict?
We all depend on the beast below.

Luc Pattyn

Hrizip wrote:

wrapper = New CallbackWrapper(Me) '{.DoOnCTS = True, .BoolData = Me.m_old_cts}

So try a multi-line approach, along the lines wrapper.DoOnCTS = True FYI: You may or may not prefer to apply a With construct. :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

Prolific encyclopedia fixture proof-reader browser patron addict?
We all depend on the beast below.

Luc Pattyn

Some overall comments: 1. I have my doubt you will ever get this to work; it looks like a lot of code is present, none of which is yours, no source and no documentation available. Normally one starts from scratch, creates a little piece of code, gets it to work, then expand it a bit, etc. That way most if not all code is familiar and in working order all of the time. You will have a lot of code, some mistakes, and not much that works I expect. 2. You can tell Reflector to show a method in a language of choice. If VB.NET is not your prime language, and maybe C# is, it may help to look at the C# code it suggests. 3. I was told there are add-ins for Reflector that would turn an entire DLL into source code right away. 4. There are programs, and web services, that translate code from one .NET language to another. I use them occasionally when trying to answer questions here on this forum. 5. Make Google your friend. All of MSDN and heaps of useful articles will be at your disposal, simply by entering a few keywords. :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

Prolific encyclopedia fixture proof-reader browser patron addict?
We all depend on the beast below.

Hrizip

Now thats a good tip, I was aware of the various types but I did not know how to easily fix problems like the above.

Hrizip

That was my appraisal as well, I did "fix" the pinvoke method by adding the () making bytes an array BUT as I made that change I thought to myself "that probably wont work" and so I decided to ask for help. I havent yet figured out the ins and outs of pinvoking so I am still overly cautious to change things. Love the wiki, hate the "trial and error" part of pinvoking ;)

Luc Pattyn

There is http://www.pinvoke.net[^], which is interesting, not always accurate, sometimes not complete. It does not offer a VB prototype for WriteFile! I am (or should still be) working on this article[^]; what it says about passing arrays is correct, but there is a simpler way I haven't mentioned nor fully tested yet, and that is your way. :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

Prolific encyclopedia fixture proof-reader browser patron addict?
We all depend on the beast below.

Hrizip

I seem to be learning best the hard way, every time I try learning something the easy way I end up not knowing anything. This is why I love looking at other peoples code and learning their syntax. I have done a lot of work on my own serialport classes under VB.NET so most of this code is known to me. The unknown parts being delegating and event handling. I havent found a good tutorial on using delegates under VB.net nor on event handling, but I have both present here in this code sample, now if I could (given enough time) reverse engineer this, I would end up understanding both on a relatively known problem (serial port communication). VB.net is my language of choice, but I had done some minor work in C#, I have already compared C# and VB.net reflector outputs and this did help me solve SOME of the problems, just not all. I would be interested in reflector addon that turns an entire dll into source code, I have been searching under addons for it, but I havent been able to find it, is it third party (not listed on reflectors home page)? Yeah there some sort of a plugin for VS that handles PINVOKING, I also use it a lot. Turns out that using google shake and bake solutions makes me patchwork code together without knowing WHY it works, unfortunately due to time constraints on my projects, I do the majority of things this way. AFAIK most programmers do. It makes me feel unsecure about my knowledge and the behaviour of the code that isnt all mine. I love learning how the stuff actually works.

Hrizip

Ah I have read it some time ago when I first encuntered pinvoking problems, at the time it seemed a large wall of text so I skipped over most of it, only looking at the bits that interested me, now that I have more knowledge I will read it once again. Thats the problem with really detailed articles, one should really read them more than once, and at different time, as one progresses in knowledge. Its like watching Star Wars as a kid and as an adult, different things. Things stops revolving around light sabres and Leia become interesting ;)

Luc Pattyn

IMO the quickest way to learn a new technology is by reading a book about it. A tutorial is meant to take you from zero to first understanding; you will not be getting why things are done a particular way, and not another way, just by looking at existing code. I can't help you with articles on delegates and events if you insist on them using VB examples. :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

Prolific encyclopedia fixture proof-reader browser patron addict?
We all depend on the beast below.

Hrizip

Fixed, in this case "UL" was the correct suffix to "cast" the number to UINT32

Hrizip

Fixed it!

Hrizip

Fixed!

Hrizip

Fixed a few things; 1) Delegate is a system.delegate method so there was a problem in namespaces, had to explicitly state what a "DELEGATE" is (a system.delegate in this case) 2) Unresolved at this time, mostly because I am clueless when it comes to delegates ;) This is the C# variant of one of the events/delegates:

public delegate void OnForceClose(int ErrorCode);

public event OnForceClose OnForceClose;

When expanded it reveals the following:

[MethodImpl(MethodImplOptions.Synchronized)]
public void add_OnForceClose(OnForceClose value)
{
this.OnForceClose = (OnForceClose) Delegate.Combine(this.OnForceClose, value);
}

[MethodImpl(MethodImplOptions.Synchronized)]
public void remove_OnForceClose(OnForceClose value)
{
this.OnForceClose = (OnForceClose) Delegate.Remove(this.OnForceClose, value);
}

VB.net variant looks like this:

Public Custom Event OnForceClose As OnForceClose

MethodImpl(MethodImplOptions.Synchronized) _
Public Sub add_OnForceClose(ByVal value As OnForceClose)
Me.OnForceClose = DirectCast(Delegate.Combine(Me.OnForceClose, value), OnForceClose)
End Sub

MethodImpl(MethodImplOptions.Synchronized) _
Public Sub remove_OnForceClose(ByVal value As OnForceClose)
Me.OnForceClose = DirectCast(Delegate.Remove(Me.OnForceClose, value), OnForceClose)
End Sub

I have no idea what this does, I can make an educated guess and say that this delegate is "announced" by using an older routine that does not use "add handler", "remove handler" and "raiseevent" instead it plugs into an older system.delegate method and therefore uses a different way of adding and removing a handler (see c# example). The VB example seems to show how to splice two delegates (or events) into one by the means of system.delegate.combine method, I have no idea why this is used in this example and what it should accomplish. I would need to find out what the difference is between the above mentioned examples and the addhandler/removehandler/raiseevent (which I am partly familiar with) and then try to recreate the whole thing. Any help/insight would be most welcome.

Luc Pattyn

Hi again, in normal situations, you don't need to go into the internals of events, i.e. I don't expect you would need Delegate.Combine at all. In normal circumstances, all the code you would need is what can be found in the MSDN example here[^]. There are three parts: 1. event declaration, with event keyword 2. event set-up, based on AddHandler 3. event processing, which looks like a regular method you have to provide. :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

If you want my opinion or comment, ask in a forum or on my profile page; I will not participate in frackin' Q&A

Luc Pattyn

that would be "UI" not "UL", in .NET "long" variables take 64 bit, you don't need that, do you? :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]

If you want my opinion or comment, ask in a forum or on my profile page; I will not participate in frackin' Q&A

Hrizip

Indeed UI it is.