Migrating ASP.NET WebForms to Modern .NET
ASP.NET WebForms has no direct equivalent in modern ASP.NET Core. I migrate WebForms applications to MVC, Razor Pages or Blazor one page at a time, so the business keeps running while the code gets better.
Why WebForms is hard to move
Pages and server controls
The page lifecycle, server controls and ViewState have no direct equivalent in ASP.NET Core. The user interface has to be rebuilt, not converted.
Logic mixed with the page
Business rules often live in code-behind files, tangled with the screen. The first step is to pull them out so they can be tested and reused.
Old components
Third-party controls, old AJAX libraries and WebForms-specific tooling tie the system to the old stack and make every change slower.
Where to move it: MVC, Razor Pages or Blazor
ASP.NET Core MVC or Razor Pages
The closest to how WebForms applications already work: server-rendered pages. Usually the lowest-risk target for business applications with many forms and grids.
Blazor
A component-based interface written in C#. A good fit when the team wants to keep working in C# and the application is very interactive.
Which one fits depends on your team, your screens and how interactive the application needs to be. We decide it together during the Audit, not before.
How the migration works
- Take stock List the pages, the shared code, the dependencies, the authentication and the session state.
- Put the new application in front An ASP.NET Core application receives every request and forwards the ones that have not moved yet to the old WebForms application. Microsoft documents this approach for migrating ASP.NET Framework applications.
- Move page by page Start with the pages that are least risky or most valuable, and extract the shared logic into libraries both applications can use.
- Retire the old application When the last page has moved, remove the forwarding and the WebForms application.
I use AI-assisted development to move faster, and every change is reviewed and tested.
What usually needs its own plan
- Sign-in shared between the old and the new application, and Windows Authentication in particular.
- Session state and anything stored in ViewState.
- Reports and exports built with legacy components.
- Third-party controls that have no version for modern .NET.
- Scheduled tasks, deployment and the database scripts that go with the application.
Where to start
From USD 2,000, fixed.
The Audit reviews your WebForms application in one week and gives you the risks, the target architecture, a phased roadmap and a cost estimate. You decide what to do with the report.
Experience
- More than 20 years working with .NET, including the WebForms, jQuery and VB.NET era at HotelDO.com (2005–2014).
- At HotelDO.com I built and maintained the core booking and CMS systems of a major online travel agency, used by thousands of people every day.
Frequently asked questions
Can WebForms run on modern .NET?
No. ASP.NET Web Forms is not part of modern ASP.NET Core, so the pages have to be rebuilt in MVC, Razor Pages or Blazor. The business logic, on the other hand, can usually be reused.
Do I need to migrate everything at once?
No. The new application can sit in front of the old one and take over page by page, so both run in production at the same time until the last page has moved.
How long does it take?
It depends on the number of pages and on how much logic lives in the code-behind files. The Audit gives you a phased roadmap and an estimate, so you know before committing to anything.
Where do I start?
With the one-week, fixed-price Audit. You get a report on risks, target architecture, roadmap and cost, and you decide what to do next.
Is your WebForms application worth migrating?
Book a free 30-minute call and tell me about your system. We will see whether the Audit makes sense for your case.