VB6 Migration Advice [closed]

Question

I know a lot of question regarding VB6 migration have been asked, but I don't believe my exact situation has been answered in them.

Basically, our company is wanting to migrate our mission-critical VB6 Line-of-business app that is quite large, uses custom libraries to communication to other in-house programs and some dll's we don't have access to the source. No semblance of any sort of "best practices been used" with this legacy app. In fact, almost all variables are global variants and most code such as printing, etc have been just copy/pasted to where it was need. Well, copy, pasted and changed just a tad...

The decision between VB.NET and C#.NET is up to us if we should attempt migration and they would like us to cater for the possibility of shifting the application to a web-based format. Management will not spend money on external migration companies.

The other option is from our infrastructure team, which has been looking at Using Virtualization to Preserve a Visual Basic 6.0 Client-Server Application

Our boss wants us to give high-level estimates and advice, but has told us the executives would like it done by April 2010.

Yes, we laughed at that.

My questions are:

Has anyone had any experience to share with the virtualization path as this is a far preferable option from the development teams point of view? Has it worked for you? Are there pitfulls you would warn of?

Despite previous System Analysts having given estimates of 1-2 years, management constantly pushes for 2-4 month timeframes. Any advise on convincing them this is insane?

Has anyone migrated are large VB6 app to a web-app successfully? One of the previous VB6 migration questions had an answer of converting sections to .NET enabled COM libraries to hollow out the VB6 app. Could this approach be used? Has anyone here tried it successfully?

Answer 1

one piece of advice to convince them its insane is to break down the task into small units, as much as possible then give an estimate and present this to management. The reason why management often can't give realistic estimates is because they don't understand the scope of the task at hand. So if you slice and dice the tasks and let them see what actual work is needed it will be easier to convince them - or reconsider to select a subset of the tasks and have a series of releases.

with regard to 'porting' it to .net, one way to do it is to rewrite the vb6 program to modules (COM) and incorporate the functionality in a new .net app, then little by little rewrite module after module into your favorite .net language. Although by the sound of it this may be as messy as any other approach.