Your legacy app, moved to modern .NET at a fixed price, with tests that prove it still works
VB6, WebForms, WCF, Access or old .NET Framework. We rewrite it on .NET 10 with AI coding agents and 22 years of enterprise architecture, and every change is checked against how your current system behaves.
UK company based in Reading. On-site across the UK, remote across Europe.
Three services, each a fixed-price package
Priced as packages, never by the hour. We take a small number of engagements at a time, so every change gets senior review.
Legacy .NET modernisation
VB6, WebForms, WCF, Access or .NET Framework moved to .NET 10 in slices, with characterisation tests proving each slice behaves like the old system.
Fixed-price packages from £20,000
How the migration works →SecurityAI App Security Review
For apps built with Lovable, Bolt, Cursor or v0 and for LLM features: auth and row-level security, leaked secrets, OWASP Top 10 and prompt-injection tests.
Fixed package price, agreed before work starts
What the review covers →BackingTechnical backing for your team
A senior architect on call for founders and engineering leads: decisions, code and architecture reviews, hiring panels, investor questions and tech due diligence.
Fixed monthly retainer, four seats
How the backing works →Training your engineers instead? Team workshops, on-site in the UK or online, on AI-assisted modernisation and secure AI development.
Why legacy .NET is on the agenda now
Unsupported software keeps running. It stops getting security fixes, and that is what auditors, insurers and enterprise customers ask about.
.NET 8 and .NET 9 lose support
Windows Server 2016 and .NET Framework 4.6.2 lose support
SQL Server 2016 left extended support
Every date, with sources: Microsoft end-of-support calendar 2026–2029.
AI writes the code. Tests decide if it is right.
Moving a legacy application is a rewrite, not a version upgrade: the UI, WCF and COM dependencies, the data and the business rules all move. AI agents such as GitHub Copilot and Claude do much of the typing; the engineering is in proving that nothing changed by accident.
Map
AI-assisted analysis of every screen, endpoint, stored procedure and integration, including the business rules nobody wrote down.
Pin down
Characterisation tests record what the old system does today, so the new one is checked against it automatically.
Migrate in slices
Old and new run side by side. AI agents write most of the code; I review every change before it merges.
Harden and hand over
Security review, CI/CD, monitoring and documentation. Your team owns the result.
Honest numbers on what AI changes in a migration: the AI migration reality check.
I’m a software architect with 22 years in enterprise .NET. I worked on legacy .NET modernisation and security compliance at MSD Animal Health, led a multi-system modernisation programme across 20 countries for Loomis, and spent nearly four years on the architecture of Saga’s membership platform. Earlier roles took me through Schlumberger, E.ON and Škoda Auto.
Today I combine that experience with AI coding agents I have built and tuned for code analysis, test generation and review. I also build and run my own software products, which keeps my hands on real production code. MSc in Software Engineering.
I take on a small number of clients at a time, so the person you talk to is the person who reviews your code.
Guides for technical decision-makers
.NET 8 and .NET 9 End of Support (10 November 2026): What To Do Now
Support for .NET 8 and .NET 9 ends on 10 November 2026. What actually stops, what keeps running, and a practical upgrade plan to .NET 10 LTS.
Legacy ModernisationMicrosoft End-of-Support Calendar 2026–2029: .NET, .NET Framework, SQL Server, Windows Server
Every end-of-support date that matters for .NET applications in one table, with what each deadline means for security, compliance and cost.
Legacy ModernisationVB6 in 2026: Does It Still Run on Windows 11, and How Do You Migrate It to .NET?
VB6 apps still run, but the IDE has been unsupported since 2008. The real risks, your migration options and why converters stall at the last 10%.
Questions people ask first
What does SelectWise do?
SelectWise is the UK consultancy of Jan Sevcik, a software architect with 22 years in enterprise .NET. It modernises legacy applications (VB6, WebForms, WCF, Access and .NET Framework) to .NET 10 using AI coding agents guarded by characterisation tests, reviews the security of legacy and AI-built software, and gives founders and engineering teams senior technical backing.
How much does a legacy .NET migration cost?
Every engagement is a fixed-price package. It starts with a Modernisation Blueprint, from £20,000: two weeks, including one migrated screen or service and a fixed price for the full rewrite. The rewrite itself is a fixed price with milestone payments, sized to your codebase. Nothing is billed by the hour or the day.
Can AI really migrate a legacy application?
AI agents now write most of the new code quickly. They cannot tell what the old system is supposed to do, so every migration starts by recording its current behaviour in automated tests, and every AI-written change is reviewed before it merges. AI cuts the cost of a migration far more than its calendar time.
Where do you work?
SelectWise is a UK company based in Reading, Berkshire. We work on-site with clients across the UK and remotely across Europe, in English or Czech.
Find out what your legacy system really needs
A 15-minute call about what you run, which support deadlines apply, and whether a fixed-price rewrite is the right move.
Book a 15-minute callOr email jan@selectwise.io