AI-Assisted Modernization of a Retail Core System with 3.2M+ Lines of VB6 Code
Retail · Japan Market · AI-Assisted VB6 to VB.NET Migration · 15 Members · Ongoing since Dec 2025
A Japanese retailer needed to modernize more than 3.2 million lines of VB6 code while controlling migration risks across its sales, inventory, payment and peripheral functions. Newwave Solutions applied CodeShift VB – an approach combining AI-assisted remediation with engineer-led validation and physical device testing. The approach reduced repetitive correction work, controlled migration risk and created a more maintainable foundation for the system.
Client Context
The client is a Japanese retailer specializing in tools and hardware products. Its daily operations depend on a Windows-based POS core system that connects product and master data with purchasing, sales, returns, payments, inventory, accounts payable and periodic reporting.
Because these functions are closely connected, the application plays a critical role in maintaining accurate transaction, inventory and financial data across the business.
Industry
Retail
Market
Japan
Team
15 members
Services
AI-Assisted VB6 to VB.NET Migration
Business Stakes
The client’s business critical POS platform had become increasingly difficult to sustain on VB6, while its scale, behavior differences and hardware dependencies made manual modernization costly, slow and operationally risky.
The VB6 environment was approaching the limits of support, while engineers with the skills to maintain it are becoming harder to secure. Remaining on the legacy platform would make future business changes increasingly difficult, creating the need for a more stable and maintainable foundation for long term operations.
The application contains more than 3.2 million lines of code (904,622 lines of business logic and 2,353,718 lines of UI code). Migrating and correcting this volume manually would require substantial time, capacity and cost.
VB6 and VB.NET handle namespaces, classes and default behaviors differently. If these differences are not identified and controlled, migrated functions could behave differently from the existing system, affecting connected sales, inventory and reporting workflows.
The POS system connects to barcode printers, scanners, receipt printers, cash drawers and other physical devices. Replacing legacy device libraries requires careful evaluation and physical testing. Without adequate compatibility validation, device issues could affect transaction processing at retail counters.
Our Approach
With over 3.2 million lines of code, correcting every conversion issue manually would require significant time, cost and engineering capacity. It would also make remediation inconsistent across a system that supports connected retail processes, from sales and payments to inventory and financial reporting.
Newwave Solutions therefore applied the CodeShift VB Approach, where AI supports the identification of recurring conversion issues while engineers remain responsible for evaluating business logic, managing behavior differences and making final quality decisions.
More about CodeShift VB Approach: https://newwavesolution.com/convert-vb6-to-vb-net/
CodeShift VB Migration Process
Step 01 | Establish the Baseline
Convert VB6 code to VB.NET, then categorize conversion errors to prioritize remediation across the codebase.
Step 02 | Build Reusable Remediation Patterns
Analyze recurring errors and apply AI-assisted rules to fix them at scale, minimizing repetitive manual work.
Step 03 | Validate and Govern Business Behavior
Test migrated functions against business logic and align VB6–VB.NET behavior differences with the client.
Step 04 | Verify Code and POS Compatibility
Review AI output and validate integration with physical POS peripherals using suitable .NET libraries.
Technical Decisions
The central technical decision was to combine AI-assisted code conversion with engineer controlled validation, allowing the team to improve migration efficiency while protecting critical retail behavior and POS compatibility.
Visual Studio Migration Wizard
The wizard served as an initial conversion tool that helped the team identify affected areas and prioritize remediation early.
CodeShift VB
CodeShift VB combined AI assisted pattern recognition with predefined remediation rules. Recurring issues involving unsupported namespaces, classes and behaviors could be corrected consistently, reducing repetitive engineering work across the codebase.
Engineer Validation Gates
Automated output was not treated as final code. Developers reviewed the migrated source and tested individual business functions, ensuring that decisions affecting sales, payments, inventory and reporting remained under human control.
Japanese Target Environment
Testing was performed on Windows 11 x64 with Japanese fonts and SQL Server 2019 Express Japanese version. This aligned validation with the client’s target environment and helped identify locale related behavior during migration.
During each project phase, Newwave Solutions and the client held a weekly review covering completed work, current issues, and the plan for the following week. Additional sessions were arranged whenever business workflows, behavior differences, or POS peripherals required closer discussion.
Both sides worked as one project team. The client prepared screen flows to support system analysis and business testing, while also assisting with the setup of physical POS devices. Newwave Solutions maintained detailed plans, controlled change requests, and assessed the schedule impact of emerging issues before adjusting the delivery plan when required.
Beyond the agreed scope, Newwave Solutions also produced additional documentation on the migration flow and the migrated source-code structure. This was prepared proactively so that the client's own team could understand the new system and take over maintenance independently after handover.
Risk Handling
Peripheral compatibility was one of the most significant migration risks. Replacing these with .NET equivalents was not a straightforward substitution, since differences in library behavior could change how the migrated application interacts with physical hardware.
To manage this, Newwave Solutions coordinated with the client to set up a test environment in Vietnam equipped with the required POS devices — barcode printers, scanners, receipt printers and cash drawers. The tests confirmed that the required peripheral functions performed consistently with the legacy system.
Product Outcomes
The team achieved 1,500 LOC per person per day for business logic and 7,000 LOC per person per day for UI code. Pattern based remediation reduced repetitive manual corrections and supported more efficient delivery across the large codebase.
Behavior differences were documented, categorized and reviewed with the client, enabling each case to be handled through an agreed remediation path. This structured approach shortened research and decision-making time on recurring behavior issues, and kept remediation cost lower than resolving each case individually from scratch.
Physical testing confirmed that the required barcode printers, scanners, receipt printers, cash drawers and all client-provided peripheral devices tested to date could operate successfully in the .NET environment. This reduced a major source of migration and operational risk.
The client received documentation and knowledge transfer covering the migration workflow and source code structure. This provided a clearer foundation for maintaining the system after handover.
Business Impact
The value of the migration went beyond replacing VB6 with VB.NET. By combining CodeShift VB’s AI assisted remediation with engineer led review, the team reduced repetitive correction work and improved coding productivity compared with a fully manual migration approach. Business testing and controlled behavior remediation also helped preserve the logic behind sales, inventory, payments and reporting.
Testing with physical POS devices in the .NET environment reduced uncertainty around peripheral compatibility, verifying that client-provided printers, scanners and other equipment could operate with the migrated application. Together with documentation on migration workflows and source-code structure, this positions the client team to take over operation, maintenance and future improvements once the migrated system is handed over.
Throughout the ongoing engagement, the client has expressed satisfaction with the quality of the migrated output, the delivery pace, and the overall cost efficiency of the project.
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