VB6 to C# Modernization for an Insurance Administration Platform: 327 Files, 242K+ COM Calls Eliminated

Results at a Glance

Engagement Snapshot

About the client:

The client is a major insurance administration provider offering integrated retirement, investment, life, and insurance solutions. Their core system, built on VB6 with a complex architecture of multiple executables, DLLs, and COM dependencies, had become a bottleneck limiting scalability, maintainability, and integration with modern technologies.

The client sought a structured modernization approach to migrate the entire VB6 platform to a fully integrated C# environment without losing any of the business logic embedded across 327 files and 242,613 COM interactions.

Challenge

The client’s VB6 insurance administration platform was one of the most structurally complex legacy systems Legacyleap has encountered, with five compounding constraints:

242,613 COM Component Calls Creating .NET Incompatibility

The system made 242,613 calls to external COM components. Every one of these calls represented a dependency that was incompatible with modern .NET frameworks and had to be systematically identified, mapped, and replaced. The sheer volume meant that manual elimination was not viable. It required automated analysis to even understand the full scope.

327 Files Across 259 Forms and Multiple MDI Components

The platform spanned 327 files, including 259 forms and multiple MDI (Multiple Document Interface) components. This scale made enhancements cumbersome, troubleshooting slow, and any modernization effort a massive undertaking in terms of surface area alone. Every file had to be analyzed, transformed, and validated individually.

9,612 Control Instances Causing Performance Constraints

Over 240 unique UI containers held 9,612 control instances across the platform. This density of controls created performance constraints. Slow rendering, excessive memory consumption, and UI responsiveness issues affected daily operations for insurance administration staff.

No Automated UI Testing Framework

The system had no automated UI testing capability. All functional testing was manual, which meant that regression coverage was incomplete, testing cycles were slow, and the risk of introducing defects during a migration of this scale was extremely high. For 327 files and 259 forms, manual testing alone could not provide adequate coverage

ADODB and Legacy Office Integration Dependencies

The system relied heavily on ADODB for data access and on legacy Excel and Word integrations for reporting and document generation. These dependencies had to be carefully replaced with modern .NET equivalents, not just removed, because the insurance administration workflows depended on the specific behavior of these integrations.

How Legacyleap Eliminated 242,000+ COM Dependencies Without Rebuilding From Scratch

Legacyleap executed a comprehensive, automation-driven modernization that transformed the entire VB6 platform into a scalable C# environment while preserving all business logic.

Phase 1: Gen AI-Powered Dependency Mapping and COM Analysis

Legacyleap used Gen AI to map the full dependency landscape across 327 files and 242,613 COM calls. This analysis identified every external COM component interaction, ADODB dependency, Office integration, and MDI relationship, creating a complete migration map that prioritized high-impact components for early transformation. Without this automated analysis, understanding the scope of 242,613 COM calls alone would have consumed months of manual effort.

Phase 2: Automated COM Elimination and Code Transformation

AI-assisted tools systematically replaced all 242,613 COM-based component calls with native .NET alternatives. ADODB was replaced with modern .NET data access patterns. MSFlexGrid controls were replaced with .NET equivalents. Gen AI models refactored and optimized legacy business logic throughout the transformation, ensuring functional parity at every step. The approach was elimination by replacement, not rebuilding from scratch.

Legacy Office Integration Replacement

The system’s reliance on legacy Excel and Word integrations was deeply embedded in insurance administration workflows — policy document generation, reporting, data exports, and bulk processing all depended on these integrations. 

Legacyleap replaced each Office integration with modern .NET equivalents that preserved the exact functionality insurance staff relied on. This was handled as a distinct workstream because the Office dependencies touched different parts of the architecture than the COM calls and required specialized replacement strategies for each integration type.

Phase 3: Architecture Consolidation

The migration consolidated 5 EXEs and 10 DLLs into a streamlined .NET environment. This consolidation eliminated the fragmented architecture that had made the legacy system difficult to maintain, deploy, and extend. The modernized architecture uses lightweight, object-oriented C# coding standards with extension methods for VB6 compatibility where required during the transition period.

Phase 4: Automated UI Testing Framework

The client’s most painful constraint was the complete absence of automated UI testing. Legacyleap built a custom automated testing solution enhanced with Gen AI-generated test scripts. This framework provided regression coverage across all 259 forms and 327 migrated files, something that manual QA could never achieve at this scale. The automated testing framework reduced functional testing time and ensured high reliability across the entire modernized platform. This capability did not exist before the engagement and now serves as a permanent asset for the client’s ongoing development.

Phase 5: Performance Optimization

With the 9,612 control instances rationalized and the COM overhead eliminated, the platform’s performance constraints were resolved. AI-driven performance analysis fine-tuned database queries and memory management, and the streamlined .NET architecture delivered improved execution speeds and reduced system overhead compared to the legacy VB6 environment.

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