VB6 to .NET migration: Key considerations

Abto Software
4 min readMar 25, 2024


This post is a quick overview of an Abto Software blog article.

Business leaders that utilize legacy applications built upon VB6 (Visual Basic 6) are moving towards migration. The platform’s mainline support was discontinued in 2008, which means older applications that have VB6 code are running under limitations and might require workarounds to function as expected.

Let’s talk VB6 to .NET migration and dive deeper into the process from a technical point of view.

VB6 to .NET conversion: Proven tips to maintain your efficiency

Tip 1: Code assessment

Identifying challenges

Initial assessment enables engineers to pinpoint potential challenges and bottlenecks before materialization. By comprehending the intricacies of the current codebase, the team can foresee potential issues and adopt proactive strategies to tackle them effectively.

Estimating efforts

In-depth examination offers engineers valuable insights into the upcoming project’s proximate scope and tasks. By understanding the efforts, encompassing skills, cost, time, documentation, maintenance, and even stakeholder engagement, the team can plan their workload more effectively.

Prioritizing tasks

Assessing existing legacy systems facilitates thoughtful task prioritization and data-driven resource allocation. This ensures that efforts are concentrated on most critical areas of the analyzed codebase, which require immediate attention — high-risk components, outdated dependencies, and more.

Informing strategy

Assessing existing legacy systems informs decisions about approaches, technology, methodology, and more. This means the strategy can be precisely tailored to address the challenges prior identified during discovery, thereby ensuring seamless transitioning.

Tip 2: Code preparation

Removing needless, dead code

  • Automatic assessment, which involves using specialized automated tools to identify unused code
  • Manual assessment, which involves human validation to identify irrelevant code, considering context, business logic, and dependencies

Upgrading syntax and controls

  • Syntax upgrade — the upgrade of syntax, for example the replacement of constructs
  • Control upgrade — the resolution of control-related compatibility problems, for example the migration of controls to equivalents

Fixing ambiguous data declarations

Fixing so-called data declarations means improving application robustness when handing VB6 to .NET migration by enforcing variable declaration and providing type declarations, thereby eliminating potential ambiguity.

Optimizing overall algorithmic efficiency

Optimizing the algorithmic efficiency means enhancing fundamental logic when covering VB6 to .NET migration to identify and address existing bottlenecks, thereby facilitating application performance.

Evaluating existing error-handling mechanisms

When approaching similar projects, it’s important to review and align the adopted error-handling mechanisms. With structured error-handling constructs, you improve exception handling and refine failure modes.

Conducting testing

When handling such projects, don’t underestimate unit testing, integration testing, and careful system testing. By covering all these, you enhance application performance and eliminate potential inconsistencies.

Documenting changes

During migration, it’s recommended to record every change to ensure 100% transparency and traceability, improved communication and collaboration, enhanced maintainability, and better knowledge transfer.

Prioritizing security

When migration, it is also critical to identify and address potential vulnerabilities by performing security audits, updating protocols, validating inputs and reinforcing access controls.

Tip 3: Risk management

Another recommendation — don’t underestimate risk mitigation when performing VB6 to .NET migration.

A quite generic statement, but still, when moving towards modernization, in particular VB6 to .NET migration, your team should cover risk management, as this helps diminish reputational and financial damage.

In order to eliminate:

  • Cost and time overruns
  • Skills and resource constraints
  • Data loss
  • Data corruption and duplication
  • Security vulnerabilities
  • Compatibility issues
  • Functional regression
  • Performance degradation

Your team should perform:

  • Risk identification and analysis
  • Risk mitigation strategy planning
  • Security practices — data encryption, access controls, data anonymization, data backup and recovery
  • Thorough testing
  • Performance optimization
  • Performance monitoring and review

Tip 4: Quality assurance

Quality assurance is critical to ensure the client is not:

  • Obtaining an unreliable application
  • Experiencing unjustified support expenses
  • Missing opportunities for future business growth and competitiveness
  • Facing penalties and liabilities associated with regulatory non-compliance

Quality assurance is performed to enable the client to harness:

  • Data integrity
  • Risk management
  • Application functionality
  • Regulatory compliance

First migrate, then rewrite

The decision to embark on migration typically signifies the application is mission-critical for the client company. The embedded business logic and rules often form the cornerstone of the client’s operations, which indicates it’s imperative to preserve them during the migration.

It may be tempting to use the migration to rewrite code segments of the legacy application for modernization, but that can lead to delays in time-to-market, cost overruns, technical complexity, and other associated issues. Once migration is executed, there still will be ample opportunities to optimize and expand the application without introducing unnecessary complications.

Summing up

Abto Software is there to help business leaders move towards market dominance by handling VB6 migration. Our engineers cover everything from initial code assessment to successful VB6 migration and finalization, making sure your applications are running as expected.

Contact us to determine the strategy that will best suit your objectives.

Our services:

  • Business analysis and consulting
  • Project setup and kick-off
  • Code migration
  • Code finalization
  • Acceptance testing and improvement
  • Quality assurance and deployment

Your benefits:

  • Higher performance and efficiency
  • Expanded functionality and scalability
  • Improved security through updates and patches
  • Enhanced compatibility across platforms and devices, and more



Abto Software

We empower customers business with innovative software by applying science, R&D, and own IP at abtosoftware.com