VB6 to .Net Migration Approach

Introduction

Application migration from VB6 to .Net is more than just a one-to-one code conversion which may/is common understanding. It should be looked as an opportunity to realign with market, with technology, with business goals etc. etc. The major business drivers that that lead to migration are:

• Flexible solution than can be extended easily
• Integration with external systems
• Scaling up to cope with ever increasing number of users
• Adding new features and functionalities

Considering above there are multiple approaches:

• Quick and automated conversion (probably using readily available tools)
• Re-architecting – Green field approach
• Re-architecting – hybrid approach

Approaches
Quick and automated conversion, in my view is a dirty way of conversion and there are lots of tools – open source and commercial - available in market to do this. But still they do not do 100% job, you have to tweak the code after conversion. The biggest draw back in the approach is you do not get the opportunity to take advantages from new technology and realign. All coding sins from earlier code base gets percolated to new code base. You do not get the chance to understand the code which can have impact on bug-fixing turnaround time. Moreover the coding conventions/standards and imposed by the tools which may differ significantly from your organizations coding standard.

 

Both the re-architecting approaches provide opportunity to take a fresh look towards system. It use different architectural styles like layered/N-tier, Domain Driven Design, SOA rather than typical VB6 traditional Client-Server architecture style. The better suited style can be decided only after thorough assessment. There is a slight difference between Re-architecting – Green field approach and Re-architecting-hybrid approach. The hybrid approach is open to use few existing components which are well designed, fairly stable, cohesive in nature and can be re-aligned with new architecture. Green filed approach is to throw away everything, which in my view is little harsh . The figure below shows very high level execution plan for re-architecting approach.

 

 

 

Conclusion
Above section described approaches that can be taken for migration, with my inclination towards Re-architecting-hybrid approach. The details about technology stack, architectural style, tools and platform can be decided only after better understanding of the product.