Migration of a VB6 application

Migation of a VB6 appli开发者_如何学Pythoncation to .NET platform is almost like a rewrite, no matter it is VB.NET or C#. Do you think it will require more effort to do it in Java platform, when compared to .NET platform, since it is a rewrite anyway? Please share your thoughts!

No offence, but you are wrong. Porting to .Net is usually far easier than a rewrite.

Here's the official advice from Microsoft UK:

Performing a complete rewrite to .NET is far more costly and difficult to do well [than converting] ... we would only recommend this approach for a small number of situations.

From a blog post by a Microsoft guy who consulted on rewrites:

Many companies I worked with in the early days of .NET looked first at rewriting driven in part by a strong desire to improve the underlying architecture and code structures at the same time as they moved to .NET. Unfortunately many of those projects ran into difficulty and several were never completed. The problem they were trying to solve was too large

I recommend the following two steps in this order.

1. Write down the reasons for migration or rewriting. What benefits will it bring? The benefits might be just to keep the development team happy - that might even be a good enough reason, I don't know. Make sure you know, and your managers/users agree.
2. Check out the Microsoft UK advice with a screencast explaining the 5 basic options for .Net migration. Decide which is best. It may be rewriting, but go into it with your eyes open.

In answer to your actual question: would a complete rewrite be easier in .Net or Java? That mainly depends on which one your team knows best. It also depends a little on whether the application interacts with COM, just like SLaks says.

The effort of rewriting a VB6 app is more than just a question of which language you're targetting. VB apps often rely on COM objects and certain VB-specific library methods which may not have equivalents in Java - but may have some portability in .NET.

Unless you are willing to abandon all of the dependences of the project, you may find .NET an easier target to re-write for, especially if you need to preserve some of the behavior of the existing application which derives from libraries or other dependencies.

Another consideration will be which platform your team is most familiar with - if you have a lot of Java expertise but little or no .NET expertise, then perhaps Java is a good choice for you.

There are tools available that will migrate from VB6 to VB .Net, including the one built into Visual Studio. This tool migrates VB6 to C#. Whatever tool you use, you will still need to do a lot of manual work on the code that the tool outputs, however this is likely to be less work than a complete java rewrite.

Depending on your existing application's architecture, and how well the code is structured, you may decide it is better to completely re-design and rewrite it anyway, in which case there may not be much to choose between .Net and java.

It is important to reduce not just the total effort during migration but also the cost of maintenance after migration. Many factors drive TCO, but all things being equal I think the .NET tools, community, framework, and C# language meet or beat Java in terms of developer productivity, operational managability, and performance -- assuming your are targeting windows OS.

I do not think ease of keeping COM should be the deciding factor either. In fact, I think migrating VB6 to .NET but keeping COM when you do not have to defeats a critical purpose of doing a VB6 migration in the first place: to reduce development costs and risks by moving to a well-supported and viable platform. I will tell you why:

• Most of the popular COM libraries and controls that were used with VB6 have not evolved in many years; many of the smaller vendors have disappeared or if they are still supporting their wares, they now also offer new and improved .NET versions.

• Living with old COM after migration means living with additional complexity in terms of debugging, builds, and deployment. Also beware that COM components do not really "speak" .NET (i.e they do not use .NET types and conventions) so their use with .NET usually results in added complexity in the coding and design.

• There still are a few hold-outs and exceptions to this rule and a .NET replacement is not the always best choice, but in general, migration teams will be able to find at least one .NET replacement option for almost every COM component they use. Taking the time to thoughtfully evaluate, select and upgrade to one of those options will pay off after the migration.

• You will not want to interop anything that is VB6 you plan to migrate. Interoping your own code will lead to a longer, complex transition and typically requires back-tracking and reworking/retesting already migrated codes. Clearly this is not the most efficient and understandable upgrade path.

One more point about having to do "a lot of manual work on the output". The Great Migrations product is a new, programmable migration tool. It is designed to help migration teams incrementally improve the quality of generated code and thus reduce the manual work required to complete the migration project. This includes making the translations more correct, dealing with complex multi-VBP migrations, and also automating the restructuring of VB6/COM code to use .NET components. These features are particularly helpful if the VB6 codebase is very large, changing frequently, and being significantly re-engineered and cleaned up during the migration. This is an agile migration methodology we call the tool-assisted rewrite.

Disclaimer: I work for Great Migrations.

If the application uses COM, it will be far easier to rewrite it in .Net than in Java. Otherwise, it will probably be somewhat easier to port to .Net.

For a more specific answer, please provide more details about your application.

You could also use Jabaco it is a Java Bytecode compiler and it has it's own IDE and syntax very similar to VB6 (nearly the same).
You can find more information at:
http://www.jabaco.org/
http://www.jabaco.org/board/

use a migration tool, like ArtInSoft to just migrate it to .NET.

You can migrate the VB 6 application using the in built VS migration to VB.Net. Try to see if that helps you. If you are looking at migrating VB 6 to C# then I would also recommend what ScaleOvenStove user has recommended.