Timeline: 2025 · Category: 💼 Professional

Throughout 2025, I migrated multiple utility applications from .NET Framework 4.x to .NET 9 with stable rollouts across DEV, QA, and PROD environments.

This was a critical modernization effort affecting core business utilities that had been running on legacy frameworks for years.

The Situation

A set of internal utility applications had been running on .NET Framework 4.x for years. They worked, but maintenance was becoming painful — outdated dependencies, security concerns, and the knowledge that Microsoft’s focus had shifted to modern .NET.

The challenge: migrate without breaking anything, while keeping the applications running in production.

What I did

Analysis & Planning

  • Audited all dependencies and identified migration blockers
  • Created compatibility matrix for third-party libraries
  • Planned phased rollout to minimize risk

Technical Implementation

  • Converted projects to SDK-style format
  • Replaced deprecated APIs with modern equivalents
  • Updated NuGet packages and resolved version conflicts
  • Implemented proper Dependency Injection patterns
  • Modernized configuration (appsettings.json, Options pattern)

Rollout & Validation

  • Staged deployment: DEV → QA → PROD
  • Comprehensive regression testing at each stage
  • Performance benchmarking to catch any regressions
  • Documented all changes for future maintenance

Results

  • 40% faster build times — SDK-style projects and improved tooling
  • Simplified deployments — single-file publishing, cleaner CI/CD
  • Future-proof — ready for .NET 8, 9, and beyond
  • Better maintainability — modern patterns, cleaner code structure

Tech Stack

C# · .NET 6/8 · ASP.NET Core · MSBuild · NuGet · Azure DevOps · Git