Welcome!

Microsoft Cloud Authors: Nick Basinger, Kevin Benedict, Pat Romanski, Liz McMillan, Lori MacVittie

Related Topics: Microsoft Cloud

Microsoft Cloud: Article

Converting VB6 to VB.NET, Part I

A Look at Your Options and When to Use Them

If you're one of the many who have VB6 code, you have three basic options: stay with VB6, convert to .NET, or rewrite from scratch. In this article, we will look at converting VB6 code to VB.NET and C#. I'll discuss when it makes sense to convert versus staying with VB6 or rewriting from scratch. I will cover what converts well and what does not, different ways to do the conversion, how to get code ready to convert, and handling issues after the conversion.

Executive Overview
First, let's get an executive-level overview of where VB6 and VB.NET are at in their life cycles. Note that when I mention VB.NET in this article, I mean all three versions (2002, 2003, 2005). When I talk about a specific version, I will specify the version (such as VB.NET 2002). With the advances in VB.NET 2003, as well as its compatibility with VB.NET 2002, there is little reason to migrate to, or stay with, VB.NET 2002. VB.NET 2005 is still an unstable beta, so the focus here will be on converting to VB.NET 2003.

For those of you who wish to stay with VB6, the key fact is that VB6 developer licenses are perpetual, so developers who have licenses can continue to develop in VB6 for as long as they wish. However, VB6 was released in January 1999 and is approaching six years of age. As a result, it is near the end of its life (VB 1.0 was originally released in 1990). VB6 no longer exists as a stand-alone product - mainstream support ends in about six months - and all support will end three years after that. Currently, to get a new VB6 license, you must either buy VB.NET and then request a VB6 downgrade disk (for about $20), or get an MSDN subscription and download it from the archives. However, I wouldn't be surprised to see these dates extended.

VB6 can be a viable option for small- to medium-sized programs with limited lifespans, for several years to come. But for large, long-term projects that will need to be maintained for a number of years, VB6 is rapidly becoming a non-option.

VB.NET was in widespread beta, with some commercial applications shipping in 2001. Release 1.0 came in 2002 and version 1.1 showed up in 2003. VB.NET is clearly ready for primetime. As a bonus, Mainsoft Corp., Mono, and Portable.NET are preparing to take VB.NET code cross-platform.

VB.NET can be cheap; many VB6 developers are MSDN members and already have access to VB.NET. The stand-alone VB.NET product is about $110, and adventuresome folk can download a free copy of VB.NET 2005 that contains the upgrade wizard at lab.msdn.microsoft.com/vs2005/get/default.aspx. A DVD (or CD) of the VS2005 Enterprise version beta can be ordered for a shipping and handling fee from the same Web page. Serious developers and corporations will typically have one of the more expensive MSDN subscriptions and access to all of this and more.

Options
If you have VB6 code, your main choices are to stay with VB6, convert the code to VB.NET or C#, or rewrite the code from scratch in VB.NET, C#, or Java. If you plan to rewrite in Java, you are probably reading the wrong article (and probably the wrong magazine; may I suggest our fine sister publication JDJ).

Whether or not to convert a program is always a case-by-case decision, driven by several competing factors such as the quality of the original code, cost, programmer availability, customer base, etc. On one hand, the only clear case where not going through at least a trial conversion would make sense is if the product is at the end of its life, with only bug fixes being implemented, and no plans for future versions. On the other hand, few large VB6 programs will convert to VB.NET without some significant rewriting. In almost all cases, I think going through at least a quick "probe" conversion is a good exercise for almost all projects - even if the converted code is not used, some valuable lessons will be learned.

Although the focus of this article will be on VB6 to VB.NET conversions, those of you moving to C# or looking at a complete VB.NET rewrite can still benefit from a conversion to VB.NET. For those of you looking at moving to C#, there are several tools (we will take a quick look at a couple of them later) that convert VB.NET to C# (and back), so it makes sense to convert to VB.NET as a step on the way to C#. If you're planning to do a complete rewrite to either VB.NET or C#, you can use the VB.NET conversion wizard to get a head start. In most programs, there are blocks of code that implement algorithms or business logic. These blocks of converted code can be pasted into a new project, speeding development for those choosing to do a complete rewrite.

Also consider that there are different levels and methods of conversion. If you have an ActiveX control written in VB6, a true conversion would be to rewrite it as a WinForm control in VB.NET. A better option might be to wrap the control in a .NET wrapper and use it from .NET while converting and testing. Shipping a VB6 ActiveX control with a .NET application can complicate the install because the VB runtime and associated files must also be installed. This is the same installation that is required if the control is installed with a VB6 application, but it is obviously more complex than the simple XCopy install of pure .NET applications.

Another way in which this ActiveX wrapper trick can be used is on forms that do not convert well, regardless of the reason. If the form can be moved to a separate project that was created as an ActiveX control project, the resulting ActiveX control can be added to a replacement form in VB6 or to a VB.NET project. Any form that can be separated from the rest of the program in this manner can be converted to an ActiveX control and used from .NET using .NET's built-in interop capabilities. In addition, we will see that most simple DLLs can be easily used directly from .NET.

In converting from VB6 to VB.NET 2003, three areas will be looked at: general VB6 code, ADO database code, and ASP Web page code. In this article, I concentrate on using the upgrade wizard to convert general VB code to VB.NET. In the future articles, I will finish general conversion issues, covering ADO, ASP, C#, and VB.NET 2005.

Before We Even Start
Remove dead code; you cannot have trouble with code you do not convert. Remove variables that are never used and subroutines that are never called. I converted one application that was large enough to have a number of associated programs, such as configuration programs, format converters, upgrade tools, and some ActiveX controls. Most of these utilities shared header files (WIN32 API declare statements and user type definitions) with the main application, but most of these programs only used a few of the functions in the headers. Other applications did not use anything in some of the headers. By removing the unused files and functions from the project, I was able to convert all the utilities much quicker. This allowed some functionality to be shown quickly, and provided the experience needed to tackle the main application.

More Stories By Dennis Hayes

Dennis Hayes is a programmer at Georgia Tech in Atlanta Georgia where he writes software for the Adult Cognition Lab in the Psychology Department. He has been involved with the Mono project for over six years, and has been writing the Monkey Business column for over five years.

Comments (2)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


IoT & Smart Cities Stories
Never mind that we might not know what the future holds for cryptocurrencies and how much values will fluctuate or even how the process of mining a coin could cost as much as the value of the coin itself - cryptocurrency mining is a hot industry and shows no signs of slowing down. However, energy consumption to mine cryptocurrency is one of the biggest issues facing this industry. Burning huge amounts of electricity isn't incidental to cryptocurrency, it's basically embedded in the core of "mini...
Every organization is facing their own Digital Transformation as they attempt to stay ahead of the competition, or worse, just keep up. Each new opportunity, whether embracing machine learning, IoT, or a cloud migration, seems to bring new development, deployment, and management models. The results are more diverse and federated computing models than any time in our history.
At CloudEXPO Silicon Valley, June 24-26, 2019, Digital Transformation (DX) is a major focus with expanded DevOpsSUMMIT and FinTechEXPO programs within the DXWorldEXPO agenda. Successful transformation requires a laser focus on being data-driven and on using all the tools available that enable transformation if they plan to survive over the long term. A total of 88% of Fortune 500 companies from a generation ago are now out of business. Only 12% still survive. Similar percentages are found throug...
Japan DX Pavilion at @CloudEXPO Silicon Valley
The graph represents a network of 1,329 Twitter users whose recent tweets contained "#DevOps", or who were replied to or mentioned in those tweets, taken from a data set limited to a maximum of 18,000 tweets. The network was obtained from Twitter on Thursday, 10 January 2019 at 23:50 UTC. The tweets in the network were tweeted over the 7-hour, 6-minute period from Thursday, 10 January 2019 at 16:29 UTC to Thursday, 10 January 2019 at 23:36 UTC. Additional tweets that were mentioned in this...
In his general session at 19th Cloud Expo, Manish Dixit, VP of Product and Engineering at Dice, discussed how Dice leverages data insights and tools to help both tech professionals and recruiters better understand how skills relate to each other and which skills are in high demand using interactive visualizations and salary indicator tools to maximize earning potential. Manish Dixit is VP of Product and Engineering at Dice. As the leader of the Product, Engineering and Data Sciences team at D...
At CloudEXPO Silicon Valley, June 24-26, 2019, Digital Transformation (DX) is a major focus with expanded DevOpsSUMMIT and FinTechEXPO programs within the DXWorldEXPO agenda. Successful transformation requires a laser focus on being data-driven and on using all the tools available that enable transformation if they plan to survive over the long term. A total of 88% of Fortune 500 companies from a generation ago are now out of business. Only 12% still survive. Similar percentages are found throug...
Where many organizations get into trouble, however, is that they try to have a broad and deep knowledge in each of these areas. This is a huge blow to an organization's productivity. By automating or outsourcing some of these pieces, such as databases, infrastructure, and networks, your team can instead focus on development, testing, and deployment. Further, organizations that focus their attention on these areas can eventually move to a test-driven development structure that condenses several l...
The term "digital transformation" (DX) is being used by everyone for just about any company initiative that involves technology, the web, ecommerce, software, or even customer experience. While the term has certainly turned into a buzzword with a lot of hype, the transition to a more connected, digital world is real and comes with real challenges. In his opening keynote, Four Essentials To Become DX Hero Status Now, Jonathan Hoppe, Co-Founder and CTO of Total Uptime Technologies, shared that ...
Over the course of two days, in addition to insightful conversations and presentations delving into the industry's current pressing challenges, there was considerable buzz about digital transformation and how it is enabling global enterprises to accelerate business growth. Blockchain has been a term that people hear but don't quite understand. The most common myths about blockchain include the assumption that it is private, or that there is only one blockchain, and the idea that blockchain is...