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Less time consuming : Rewriting or converting an app from VB5 to C#

I've got a contract where I have to continue the development of and old application suite that was programmed in VB5 back in the days.
I've bug to fix and new feature to develop.
So I have a few choices:
Keep programming in VB5
(NOOOOOOOOOOOOOOO!!!!)
Convert VB5 to C# (How??? Is it
possible without going insane?)
Rewrite the whole application suite
(Very time consuming)
Is there any other choices? What should I do?
EDIT: Ah and also, it relies on an ACCESS database which I'd like to move to SQL EXPRESS. Because it's a crazy database made illogically by a stupid programmer from the '90s lol.
Thanks

The choice I've made every time is to just re-write, or purchase a suitable replacement if I could find one.
I have tried doing incremental upgrades from VB6 to VB.NET, but I don't like that approach because it leaves around ActiveX controls that I'd rather not use. Re-writing is cleaner.
I don't think there is a converter from VB5 to C#. You might be able to go from VB5 to VB.NET and then convert to C#, but in my experience it's less time-consuming to re-write than it is to try to upgrade and fiddle around with the broken code.

There is no reliable way to do 2) so it's 1) or 3).
And I don't think your customer wants to pay for 3). But maybe you can sell it on reliability, support etc.
Otherwise you're stuck with 1)

One approach would be to tactically rewrite sections of the code in C# - you could start with the areas you are likely to be bugfixing the most, create C# assemblies to mirror the functionality, and then expose these to the VB5 code through COM interop.
A good suite of Unit Tests would be highly recommended for this approach!
I've heard that Working Effectively With Legacy Code by Michael Feathers is the best book around for understanding how best to chop up a problem like this.

The answer definitely depends on a lot of factors. I recently had a similar project (a 10-year plus old VB6 Windows app with a large, spaghetti codebase), and addressed it with a "hybrid" approach:
Bugs were fixed in VB6
New features were developed in .NET 4, using COM interop
We developed some WPF dialogs and styled them to go with the old interface to handle new UI.
This option only works when the new features are fairly independent of the main app, but it has the advantage of at least taking advantage of the productivity of new technologies and also paving the way for future conversion.

I've recently finished working on a project where we converted a lot of legacy VB6 applications to C# using Artinsoft's VB Upgrade Companion.
It's a tough call to decide which approach is the best. In a lot of cases, converting the code can end up being very painful, especially if there is a lot of logic based around features which are significantly different between the two platforms (e.g. one-indexed arrays, or handling errors via the Information.Err object instead of through exceptions).
On the other hand, if you try to write it from scratch, there is a good chance that you'll accidentally change some subtle behaviour that isn't immediately obvious when reviewing the original VB5 code. Things like this can be difficult to track down.
A good compromise is to use a converter to port the code over, then use this as a guide for writing things from scratch, as there will hopefully be places where you can just lift converted code across straight into the new code base. At the same time though, you get the benefit of writing more maintainable code everywhere else.
With all that said, if the original VB5 is well written and (relatively) well architected, then I would recommend against any sort of upgrade. You will spend far more time trying to match the existing behaviour of the old application than you would just working on the old code.
Good luck with whatever you decide to do - you'll need it :)

Maybe you should first convert to vb.net, and then to C#?

If you just need to fix a bug, and it's a reasonably simple bug, and you don't anticipate much more work beyond that - stick with VB5. Anything else will introduce far more work.
However, if this is really a "live" product which you expect to work on a lot in the future, I would probably start from scratch. My guess is that you've learned a lot about design and architecture since writing the app - so you might as well take the opportunity to write a more maintainable app. (You'll also probably have learned which design decisions in the original app ended up being mistakes.)

Convincing legacy application VB6 developers to make the switch to C#

I know this question could be similar to others but really I'm looking for reasons why VB6 developers should switch to C#.
My company recently approved project to be written in C#, so we have a lot of VB.Net programmers, however, we have some legacy app developers as well that are in VB6. We have a time frame to re-write those apps into .Net web apps. So no matter what they will have to learn new stuff.
One of the developers today specifically asked "why should we switch to C#?"
I responded that the community largely has decided that C# is the way to go with about 80% of the examples in C#. I am a VB.Net programmer and I am excited to finally cut my teeth on C#, however, being that I'm so new I'm not sure I can answer the "why?" question. My reasons are more because I want to learn it.
So without descending into a VB verses C# I really am curious if there are any resources that I can send to these developers to calm their nerves.
Looking forward to your input!

As far as the migration over to .NET goes, better late than never! As far as my advice goes, your mileage may vary, it's worth every penny you're paying for it!
I personally believe you are making the correct choice. The first instinct for VB developers is to switch to VB.NET. That sounds entirely reasonable, but in my opinion, it's the wrong choice. You really have to break down the reasons for the switch into two categories: Why switch to .NET, and why switch to C#?
Why switch to .NET over VB6:
Multithreading in VB6 is technically possible from a programming perspective, but just about impossible if you want to use the IDE.
I do not believe you can create a 64-bit native application in VB6. That rules out a lot.
No new enhancements are being made to VB6.
OK, there are so many reasons I can think of, I'll probably just stop there.
Why switch to C# instead of VB.NET
Developers may be lulled into a false sense of familiarity with VB.NET - treating resources like they did in VB6 without understanding the full concepts. An example: you often see new converts to VB.NET setting objects to Nothing, believing that it's a magical way to release resources. It is not.
It's true that most examples are now in C#. More importantly, Jeff Richter's book is only in C# now. If you want to understand how .NET really works, IMO his book is pretty much mandatory.
In .NET, you'll find that you will use lambda expressions all of the time, especially when operating with Linq. IMO VB's verbosity really becomes a barrier to comprehension and readability here, in ways where it simply wasn't before: foo.Select(x => x > 50) is, by just about any standard, much more fluent and readable than foo.Select(Function(x) x > 50). It gets worse as the expressions get more complex.
Some of the worst practices with VB6 are impossible or at least much less accessible in C# (such as ReDim Preserve and On Error Resume Next).
VB is saddled with some syntax which makes it pretty cumbersome and confusing to use when creating general-purpose CLR libraries. For example, in C#, you use indexers with brackets[]. In VB, you use parens. That makes it pretty difficult for the user of a subroutine to tell if it's an indexer or a function. If someone tried to use your library outside of VB, the difference would be important, but a VB developer might be inclined to create subroutines which should be indexers as functions, since they look similar.
I don't have any data on this, but if you are trying to hire a good set of programmers, the best ones will generally be less inclined to work in a shop which writes VB.NET over C#. They usually fear that the code their colleagues will be generating is likely to be substandard .NET code, and let's be frank here -- there's a stigma against VB.NET developers and the quality of their code in the community. There. I said it. Let the flames begin...
As a footnote, from my perspective, VB.NET was a real missed opportunity for MS. What it should have been was a way to seamlessly convert your old VB6 code to the .NET world - with dynamic invocation and high-quality COM interop from the start. What it ended up being was a near-clone of C#'s feature set with a more verbose syntax and little to no backward compatibility. Sad, really. It locked a lot of organizations out of .NET for a long time. Then again, maybe it forced a "cold-turkey" clean break from the past...

I've done a LOT of VB6 in the past, and a lot of C/C++, and when our big .NET migration happened I had no doubts that C# was the way to go. Having said that, what the VB6 guys should really be learning is .NET, and the CLR (a proper object-oriented runtime rather than a dumb COM front-end), and not a syntax. Focus on that, and sidestep the religious war.

This may not answer your question, in fact it may even contradict your response and prove your friend right, but here is a good list of the similarities (and differences) between VB.NET and C#:
C# / VB.NET comparison
As you go down this list, you will notice just how similar the two languages have become and with each new version, there may be less and less of a reason to switch. But, in the end, if you do make the switch, the Wikipedia article pretty much summarizes the advantages that C# has over VB.NET quite well:
Wikipedia article listing advantages of C# over VB and vice versa

The VB.net events syntax seems much nicer than C#; though the lack of any means for a class to either unsubscribe all WithEvents handlers to which it has subscribed, or kill all subscriptions other objects have to its events, makes it a little tough to avoid event leaks, it's no worse than C# in that regard.
Also, in vb.net, it's possible to have a Finally handler know what exception occurred (if any) in its Try block without having to actually catch it. If any exceptions occurs in the Finally block, the original exception can be included in the CleanupFailedException (along with the other exception(s) that occurred in the Finally block). That seems like a nice advantage.

"Developers may be lulled into a false sense of familiarity with VB.NET - treating resources like they did in VB6 without understanding the full concepts." (#Markle)
I haven't used this for an argument before, but it's a very good point. When I picked up a VB.NET app written by a bunch of new-to-.net VB programmers, it was littered with legacy compatibility calls to the old VisualBasic namespace. CStr(), VbNewLine, Mid(), etc... Working in a language which isn't designed to support legacy code conversion prevents the use of those relics. (So does removing the reference to the legacy namespace, FYI.)
I switch between VB.NET and C# pretty regularly. Whenever I go from VB to C#, I think "This is different, it'll take me a few minutes to adjust." Whenever I go from C# to VB, I think "This is an inefficient programming language; there's way too much typing required, how annoying."

I think the other answers have done a good job of covering the technical points. I would also point out to your vb6 developers that there are not only more books aimed at c# and more questions on SO on c#, but perhaps more importantly to them, more job listings as well.
A quick search on SO careers:
92 job postings for c#
11 job postings for vb.net
1 job posting for vb6

reasons why VB6 developers should switch to C#
Others have given technical reasons for C# over VB.NET, but I think you are dealing with a people issue, so I'll offer what I think is the most compelling reason why the developers should prefer it:
C# developers get paid more than VB.NET developers, for doing exactly the same thinking, just typing different source code after doing that thinking
Also
ReSharper for C# is better than ReSharper for VB.NET

Other than technical / social advantage is more business oriented,
Mainstream support for VB6 already ended and Extended support which is surely expensive would end soon.
Moving to a new platform in this case make more business sense.
Also the IDE is no more supported by microsoft so in case of issue you would be SOL, and installing it on shiny new laptop might provide an unenjoyable experience.
Note that they don't need to port every application, only deprecate the part that need to be replaced with com exposed .Net assemblies.
On the other hand having experience in porting software from obsolete platform to a new one will make these guys rich, providing they are willing to learn the new platform.

The biggest advantage C# has over VB6 proper has got to be inheritance.
(OK, to be fair it's my personal favourite, so I am totally biased.)
Other advantages:
Formal accessors
Exception types (I don't think VB6 has exception types, but please correct me if I'm wrong)
Generics
Lambda expressions
And the following are more related to the .NET platform than languages themselves:
Very rich library
Visual Studio refactoring and other goodies
Finally, the popularity argument is always icky (popular <> good), but it does give an idea of the community size of each and therefore what help is available out there and what the industry is going towards in general.
Questions on SO:
[C#]: 116,337
[VB.NET]: 11,740
[VB6]: 1,897

VB6 is not fully object oriented and lacks a decent set of collections/structures. VB.Net and C# are both fully object oriented and include a decent set of collection classes as a part of .NET. .NET 2 also added generics for even more flexibility.
I would agree with those who think VB.Net is a bit superfluous - it fixed the problems with VB6 and ended up being a bit of a "me too" alongside C#. Having said that, I do a lot of COM interop and find VB.Net's old fashioned ON ERROR construct a convenient way of handling timeouts and function retries. You can do it with try...catch just it is more complex.

Questions on SO:
[C#]: 116,337
[VB.NET]: 11,740
[VB6]: 1,897
That proves nothing.
VB6 existed long before SO did. All the good VB programmers learned what they need to know and MSFT had done away with VB6. Most of the new MSFT beginners flocked to C# because of their irrational hatred of anything BASIC (that still exits - just look at Xojo) and of course MSFT marketing.
But how do they feel now with C# getting short change compared to C++ on the Windows 8 platform? (eg XNA is gone).
The market pretty much demands C# over VB.net.

What's the fastest way to convert an existing Vb6.0 win-based application into a c# win-based?

What's the fastest way to convert an existing Vb6.0 win-based application into a c# win-based?

The core language is so different, that I would have to say start from scratch, and copy only the complicated code bits. If you start from scratch you won't have to deal with all the VB6 problems, while utilizing all the C# power.
VB6 has no real classes or OOP, which makes very different from C#. Also, there is very little control on the event manager (SubClassing).
So, start from zero, copy the UI layout, and think about how would I implement this in C# in the first place, it will make your life easier.

I think the fastest would be to convert it to VB.net. Check the following question for this answer
VB6 to VB.net conversion
ans then converting it to c#. But I feel converting manually will be the better option as you can re engineer the application and may be make it simpler.

Converting the code from Visual Basic 6 to C# should best be done using an automated migration tool, like ArtinSoft's Visual Basic Upgrade Companion, which supports migration to C#.There are several reasons for this suggestion, aside from my experience with the tool.
First, even if you migrate from VB6 to VB.NET there are several language specific features in VB.NET that will not translate directly to C#. So even if you're using a VB.NET to C# converter you'll have to handle these special cases (or find a tool that handles them for you). These can include optional parameters, AddressOf functions, Visual Basic Compiler assisted operations, like Information.Err(), and Unstructure Error Handling to Structured Error Handling using Try / Catch statements. Another thing to consider is that the VB.NET compiler is limited to showing only 100 compilation errors, and compilation errors can be quite common when migrating. When moving to C#'s the compiler and other code analysis tools like ReSharper can give you a better picture of the challenge ahead, and help you detect common compilation error patterns.
Second, by migrating directly to the target language you can focus on using the features available for that language from the start, no intermediate steps. Otherwise, you'll basically end up doing two migrations when you could have focused on just one.
Third, as renick stated even though migration tools can produce hundreds or thousands of issues, most of these have relatively easy solutions. Some of them can be fixed using a find & replace function. Commercial solutions have the added advantage that they support the migration of third-party UI controls to .NET equivalents.
Also a migration can be much faster than a rewrite, you still have to write code but only for the areas where there are issues.
Granted there are applications for which a migration is not an option, but for those that fit the use case for a migration, it's a very effective means of switching platforms. You shouldn't discount the option right off the bat.

Total rewrite. MS has some migration assistance, but I believe it's VB.Net only. But why look at porting, surely you'd be better off now rewriting the app, and just interop if you have any legacy parts that you need to keep alive. And only migrate the best bits. Use this as a chance to truly improve the application.

If you need it quickly; then don't go hand cranking it - you'll miss stuff out and tear your hair out!
I investigated this product a couple of years back and I felt this product was the best. it converts from VB6 to C#. They have a free trial too.

Try ArtInSoft. This company will migrate your VB 6 code directly to C#.

Using IronPython to learn the .NET framework, is this bad?

Because I'm a Python fan, I'd like to learn the .NET framework using IronPython. Would I be missing out on something? Is this in some way not recommended?
EDIT:
I'm pretty knowledgeable of Java ( so learning/using a new language is not a problem for me ). If needed, will I be able to use everything I learned in IronPython ( excluding language featurs ) to write C# code?

No, sounds like a good way to learn to me. You get to stick with a language and syntax that you are familiar with, and learn about the huge range of classes available in the framework, and how the CLR supports your code.
Once you've got to grips with some of the framework and the CLR services you could always pick up C# in the future. By that point it will just be a minor syntax change from what you already know.
Bare in mind that if you are thinking with respect to a career, you won't find many iron python jobs, but like I say, this could be a good way to learn about the framework first, then build on that with C# in a month or twos time.

You can definitely do that to learn the class library, but I'm not sure if it's such a good idea when it comes to fundamental CLR concepts (e.g. delegates and events). You'll need to pay attention and distinguish what is strictly an IronPython feature, and what is CLR feature exposed in IronPython in a way that matches its dynamic semantics better.

If I wanted to just "learn the framework", I would do it in C# or VB for two main reasons:
Intellisense - the framework is huge, and being offered suggestions for function overloads is one of the ways to find new stuff. There's almost no good intellisense for the framework with IronPython at the moment (Michael Foord has done some work on building the appropriate info for Wing, but I haven't tried it myself).
Code samples - pretty much all the educational material that exists about the .NET framework is given with C# or VB. You'll be much more on your own with IronPython.

I find .NET a lot easier to learn with intellisense. If you can get IronPython to work in Visual Studio as a first-class language, go for it. If you try, please document it!
Hmmm: http://www.codeplex.com/IronPythonStudio

Effort estimation: using C / Win32 or learning C# / .NET

I intend to write a small application to scratch a personal itch and probably make the life of some colleagues easier. Here is what I have:
10+ years of experience in C
Plenty of experience in programming against the Win16/32 API in C from the Win3.1 to 2000 days.
C library written by myself already doing about 75% of what the application shall do.
What the application shall do:
open a binary, feed it into the mentioned library.
take the resulting text output and feed it into a new Excel Workbook.
apply some formating.
integrate nicely with the Windows environment (availability in "Open With...", remember some stuff using the registry etc.)
(maybe later) before giving the CSV data to Excel, parse it by looking up the meaning of some values in an XML file.
Except for the XML parsing part I have done all of that stuff before including COM / Office Automation in C/Win32. There is a lot of boilerplate code involved, but it is doable and the result will be a pretty small application without the need for an installer.
So why even think about C# / .Net?
no experience with parsing XML
the promise of less boilerplate code for the Windows and Excel stuff (yes, I have done C++ with OWL, MFC, ATL etc. but I am not going there anymore - not for free/fun)
Since I have also experience with C++, VB(not .Net) and a little Java / Objective-C I suppose learning C# will all be about the .Net libraries and not actually about the language.
My considerations so far:
Learning .NET might be fun and might result in less code / first steps in a more modern environment.
Sticking with what I know will lead to a predictable outcome in terms of effort and function (except for the optional XML stuff)
VB looked great at the beginning until the projects where about 80% done, then the pain started and the DLL coding in C. I am concerned history could repeat itself if I choose .Net.
My primary objective is the functionality. Effort is a concern. The XML parsing is optional.
Please advice.
Update: one thing I forgot to mention explicitly is that I am also worried about easy deployment of the tool to my co-workers. With Win32 I am pretty sure I can come up with an EXE file < 1Mb that can be easily emailed and does not require installation. With .Net not so much. Can I create the necessary MSI or whatever in Visual Studio Express (free) or do I need 3rd party tools?

as others have your question mostly covered, I'd just like to quickly comment on your considerations:
Learning .NET might be fun and might result in less code / first steps in a more modern environment.
Totally agreed. It is definitely fun and usually it does result in less code. The investment you make now will certainly benefit you in future projects. It is way faster to program in .Net than in C. Not only it is easier, but it is also safer. You are isolated from many programming errors common in C mostly related to memory mismanagement. You also get a very complete managed API to do stuff you would usually need to build your own framework.
Sticking with what I know will lead to a predictable outcome in terms of effort and function (except for the optional XML stuff)
Hence your indecision. :-)
VB looked great at the beginning until the projects where about 80% done, then the pain started and the DLL coding in C. I am concerned history could repeat itself if I choose .Net. My primary objective is the functionality. Effort is a concern. The XML parsing is optional.
.Net is an entirely different beast from VB. Most of the things you wouldn't be able to do in VB, or at least do them easily, are supported by .Net. For instance, Windows Services are a snap to build in .Net. Socket programming is also supported, but there are very few reasons to do it yourself, as you've got loads of communication APIs with .Net. You've got web-services, .Net Remoting, MSMQ management, and more recently WCF. Proper multithreading is supported by .Net, unlike the idiotic apartment model in VB. In case you really need to go low level, you can also actually use pointers in C#, inside of unsafe code blocks, even though I would never advise to do so.
If you really need to do things in C, then integrating is also relatively easy. You can create COM objects and use interop to work with them from .Net. You can also interact directly with plain ol' dlls using DllImport. Using www.pinvoke.net makes it easier.
When I developed in VB, sometimes I also had to go back to C++ to do stuff that I wasn't able of doing in VB. Since I began programming in .Net, the only extremely rare scenarios I would need to go back to C++ were when I needed to use legacy COM components that used types I was having a hard time to marshal via interop. I wouldn't worry about history repeating itself.

If you're using COM, you may be interested in using C# 4.0 instead of earlier versions - the downside being that it's only in beta. But basically it makes COM stuff somewhat less ugly for various reasons.
I'd expect there to be plenty of good C libraries for XML parsing by now. I would expect the main benefit to actually be the knowledge gained. I doubt that you'll actually produce the code faster for this project, but the next one may well be a lot quicker.
How much do you care about learning new stuff?

It sounds like an ideal project for learning C# & .NET.
You know most of what you need to do so you can use that to gain a base level of understanding of C# & .NET which you can then apply to the stuff you need to learn.
As Rune says though, a key driver could be the timescales. If this is something you need in a hurry then coding it in C & using win32 directly might be the answer.
Sorry I couldn't be more definite.

I think you should use C#. With your experience the learning curve won't be too steep. The code will ultimately be cleaner (and less of it) than you probably could with C/Win32.
There is probably going to be no problem using your existing C-library with the [DllImport] attribute.

It depends. :-) It depends on whether you want to do this quickly or if you want to learn something new. It depends on whether you will be the only maintainer of the code or if others will maintain it in the future. It depends on how complex your xml handling will be and on how complex the COM automation is.
You will probably get a working application quicker if you do it in C than in C#. Both since you have much of the stuff needed already in place and since you know C well.
But this project sounds like a good match for C# and .Net. .Net has great support for XML and COM interop is easy but clumsy in C# (much better in the next version!). So if you are interested in learning C# and .Net this would be a good project to do so.
I would definitely do this in .Net and probably C# (but I am biased). Using .Net would probably result in code that is easier to read and maintain and most probably easier to write. So if you are interested in learning C# I would suggest you go for it!
Edit:
You worry about the size of the executable if you write it in .Net. I doubt that will be a problem, for most if not all of the libraries you will use for a project like this will already be installed on your computer. 1 Mb is rather large for a .Net executable, event for a big project.

a short notice on the installation. .NET is as default xcopy-able so you wouldn't need an installer for the exe to be usable. Mail it around (or with the next release of the .NET framework optionaly leave it on a network share)

You could look at building a hybrid system that uses C++/CLI and C#. C++/CLI provides a nice bridge between the two and lets you easily split different parts of the system between the managed and unmanaged worlds.
Not sure if the setup projects are included in the free versions of visual studio. But you could use clickonce (included with the framework) or WIX (open source XML based msi creation tool).

learning C# will all be about the .Net libraries and not actually about the language
No there are many things you need to learn about the language (delegates , events , generics ...) and also it is object oriented and it manages the memory by itself and yes no pointers :)
anyway C# and .NET are great all you need is some effort to get up to speed