VB6/Delphi/WinForms to .NET Core/WPF/Web SPA Migration

Firstly, audit dependencies and UX, then choose a target tech stack that fits goals and opportunities. Extract business logic into .NET class libraries via adapters, keeping the legacy UI running. Additionally, try to automate the conversion, then refactor the architecture, data access, and state. Eventually, rebuild the UI, test, and ship via containers and CI/CD.

The first step in any case is to separate the UI from the business logic. We move logic into .NET 8+ class libraries via adapters. We then change the UI. A “strangler” method helps a lot, releasing one module at a time with feature flags and contract tests to ensure everything is secure.

In this case, replace a big-bang rewrite with the migrate-then-improve approach. Move logic to .NET libraries, keep WinForms operating for now, and subsequently change the UI to a new platform. Only rewrite everything when the architecture or user experience is lagging or when third-party controls cease upgrades.

Follow this algorithm. Make a stable “contract of record”. Put old logic behind adapters, add approval or golden-master tests to lock in behavior, move logic into .NET libraries, and test it all with the same test harness. Change the UI or hosting model. Only after that.

AI tools for legacy code modernization partially handle automation. Why partially? Expect 50–80% of the syntax and project scaffolding to be automated, but 0% of the architecture and UX. Use converters to speed up stubs, and then manually refactor for globals, events, data access, and controllers from other companies.

Let’s give you an example. Here’s the following Delphi to .NET conversion tutorial.

Put work in order based on business value and risk:

1) Make data contracts stable;

2) Move core services to .NET;

3) Keep the old UI with shims;

4) Change the UI in pieces;

5) Get rid of shims.

This gets things done quickly, cuts down on freeze time, and cuts down on double maintenance.

It depends on the project specifics. Choose based on how many people will use it, if it needs to work offline, and the talents of your team, for instance:

• WPF/WinUI is best for desktops with many features, hardware, and peripherals.
• Blazor (Server/WebAssembly) is faster for .NET teams and web content.
• SPA (React/Angular/Vue + .NET API) has the biggest pool of web expertise and is best for web UX.

VB6 vs .NET Core performance varies. .NET 8 has async I/O and a modern GC, better data access (EF Core/Dapper), parallelism (TPL), and containerization for elastic scaling. On the client side, virtualization, incremental rendering, and GPU-accelerated graphics (WPF) all help speed up the UI.

Generative AI in code refactoring makes the difference. First, use a clean design and limited contexts to extract modules from a monolith. Then introduce HTTP/gRPC to enforce contracts, add contract tests, and after that, divide along natural seams like ownership and scaling hotspots. Also, you can use an API gateway or a strangler proxy to send traffic to each module. However, every stage goes smoother with AI in the game.

If you wonder how to migrate VB6 to .NET Core, see this. Apply .NET, CodeArchitects VB Migration, and Delphi’s tools for .NET as code conversion tools. At the same time, .NET Upgrade Assistant and try-convert will help you upgrade your project.

Moreover, WPF, WinUI 3, Avalonia/Uno (cross-platform), and third-party UI are all examples of desktop frameworks. In contrast, ASP.NET Core is used for web development with Minimal APIs, gRPC, Blazor, or SPA frameworks; Microsoft Identity or Keycloak helps with authentication; and Docker is employed for packaging.

WPF vs web spa pros and cons vary. First, make a design system that includes tokens, spacing, typography, and components. Pick a modern control suite that fits your brand, map old controls to new parts, and run A/B screens side by side during the migration. To keep things consistent, use MVVM (WPF) or component patterns (Blazor/SPA) and a shared style dictionary.