Every developer eventually inherits a legacy .NET project the kind where every method talks to everything, and a single change breaks three other features.
We had one of those too. And instead of rewriting from scratch, we decided to refactor and evolve it step by step. Here’s what made the difference
Started with understanding, not rewriting.
We mapped dependencies and identified the real pain points before touching a single line of code.
Introduced layers gradually.
Added separation between API, business logic, and data layers — even if it wasn’t “perfect” at first.
Applied Dependency Injection.
Breaking hard-coded dependencies gave us flexibility and made testing possible for the first time.
Moved toward Clean Architecture.
Organized the solution around use cases and domain logic, not around technical layers.
Incremental refactoring > big bang rewrites.
We refactored feature by feature while keeping the app running — zero downtime.
Added automated tests along the way.
Unit tests became our safety net for each refactored module.
Introduced modern tools gradually.
Switched to EF Core, MediatR, and background jobs via Hangfire — one at a time.
After months of iteration, we transformed a fragile legacy system into a modular, testable, and scalable architecture — without losing business continuity.
Have you ever refactored a legacy .NET project? What approach worked best for you?
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