Project Overview

We executed a project to migrate a legacy desktop application running on Windows XP on a factory production line to a Windows 10 environment. By re-architecting the existing system’s logic, originally built in VB6, using C# and .NET Framework, we eliminated the operational risks associated with the obsolete OS and completed the transition to a new system that ensures future maintainability and scalability.

Technology Stack and Development Tools Used

• Programming Language: VB6, C#
• Back-end Framework: .NET Framework
• Database: Oracle
• Communication Tool: Redmine

Client’s Challenges

Business Continuity Risk due to OS End-of-Support and Hardware Aging

The existing system was operating on Windows XP, which is no longer supported, and the hardware itself was aging. The client faced a critical risk of being unable to procure replacement hardware in the event of a failure, a problem that could directly halt the factory’s production line. From a Business Continuity Plan (BCP) perspective, resolving this situation was an urgent priority. Therefore, migrating the system to a supported Windows 10 environment was imperative. The client’s most critical requirement was that the new system must operate stably with functions and performance identical to the current system.

Client’s Requirements

Ensuring Complete Functional Parity with the Current System to Avoid Business Process Disruption

It was required that the new system replicate 100% of all existing functions and business workflows to ensure no changes or disruptions to the factory’s business processes post-migration. Minimizing changes to the user interface (UI) and operational feel (UX) was highly prioritized, allowing shop-floor operators to continue their work smoothly as before, without experiencing stress from the transition.

Adherence to Strict Coding Conventions for Maintainability and Quality, with Future Scalability in Mind

To ensure this migration was not merely a life-extension measure but also facilitated future feature additions and modifications, strict adherence to the client’s established Coding Conventions was required. Compliance with diverse rules—including naming conventions, error handling, modularization, and commenting standards—and implementing high-quality, readable, and maintainable source code were deemed essential to enhance the technical asset value of the new system.

Our Proposals and Approach

Achieving Rapid and Accurate Large-Scale Code Conversion through In-House Migration Tool Development and Utilization

The volume of source code to be migrated was enormous. Migrating it all manually posed risks of excessive labor costs, time, and quality degradation due to human error. Therefore, our company promptly developed and deployed a proprietary in-house tool to assist with the code conversion from VB6 to C#. This tool highly automated the routine and mechanical conversion processes, dramatically improving development efficiency. Concurrently, it ensured conversion accuracy consistency, thereby guaranteeing quality and contributing significantly to shortening the overall project timeline.

Mitigating Delays by Grasping Business Logic through Source Code Analysis, Independent of the Live Environment

After the project started, the delivery of the old system’s actual machine environment (Windows XP) was significantly delayed. Normally, we would operate the actual machine to understand the business workflows, but this impossibility threatened to stall the project’s progress. We immediately switched our approach, adopting a methodology of thoroughly reverse-engineering the provided VB6 source code. By directly extracting detailed processing logic and implicit business rules from the code, we completely avoided the risk of environment-dependent delays while achieving a full functional port to the new system.

Not Just “Converting and Done”: Drastically Improving Code Quality and Maintainability via Post-Migration Refactoring

The original VB6 code, as a result of repeated modifications over many years, lacked standardization and was in a state of poor readability and consistency. Merely “as-is” converting it to C# would have carried over future maintainability problems (technical debt). We incorporated a mandatory process of full code review and standardization (refactoring) after the C# conversion. By meticulously restructuring the auto-converted code and ensuring full compliance with the client’s conventions, we worked to eliminate technical debt, ensuring the new system would become a high-quality, long-term operational and maintainable technical asset.