Monday, May 12, 2025

How I Modernized an 8-Year-Old .NET Solution Using .NET Upgrade Assistant

“20+ projects. .NET Framework 4.6. Legacy dependencies. And a deadline to move everything to .NET 8.”

Recently, I began the ambitious journey of migrating an 8-year-old enterprise solution—a massive monolith with over 20 interconnected projects, built on .NET Framework 4.6, using WCF, old-school config files, and long-abandoned NuGet packages.

The goal?
✔️ Modernize the solution
✔️ Make it cloud-ready
✔️ Target .NET 8
✔️ Run cross-platform

At first, it felt like staring at a mountain with no visible trail. Rewriting everything from scratch wasn’t an option. I needed a guided, gradual approach—something to help me lift and shift without breaking everything in the process.

That's when I discovered the .NET Upgrade Assistant.

🚀 Enter: .NET Upgrade Assistant

This tool, provided by Microsoft, is a command-line utility that guides you through upgrading your existing .NET Framework or .NET Core projects to modern .NET versions (6, 7, or 8).

What makes it special is that it doesn’t just convert your project file—it walks through your entire solution, project by project, making incremental, intelligent suggestions and transformations.

📘 Official Docs:

👉 https://learn.microsoft.com/en-us/dotnet/upgrade-assistant/

💡 Why Use .NET Upgrade Assistant?

Here’s what stood out to me:

  • Step-by-step CLI guidance instead of just scripts

  • Automated backup of your solution

  • Dependency analysis and recommendations

  • Target framework upgrades to .NET 6, 7, or 8

  • Support for ASP.NET MVC, WPF, WinForms, Class Libraries, etc.

  • Great integration with modern tools like try-convert, analyzers, and Roslyn-based refactoring

🛠️ Step-by-Step: My Upgrade Journey

Step 1: Installing the Assistant

I started by installing the tool globally:

dotnet tool install -g upgrade-assistant

To ensure I always had the latest version:

dotnet tool update -g upgrade-assistant

Step 2: Running the Upgrade

I moved into my solution directory and ran:

upgrade-assistant upgrade MyLegacySolution.sln

It launched an interactive experience—asking which project to upgrade first, what changes to apply, and whether I wanted to proceed step-by-step.

The tool processed each project by:

  • Updating TargetFramework to net8.0

  • Migrating from packages.config to <PackageReference>

  • Replacing web.config with appsettings.json (for ASP.NET)

  • Notifying me of deprecated APIs

  • Updating project references

Step 3: Handling the Unexpected

Of course, some projects didn’t upgrade cleanly:

  • A few third-party NuGet packages weren’t compatible with .NET 8.

  • WCF references required rewrites or moving to gRPC or REST.

  • Some AppDomain and Remoting APIs had no direct equivalent.

For each issue, the Upgrade Assistant flagged the problem and left comments in the code or console to guide manual intervention.

I also leaned on these helpful docs:

Step 4: Testing & Tuning

After upgrading:

  • I ran all unit and integration tests (yes, we had a decent suite!)

  • Manually tested critical app paths

  • Removed obsolete dependencies

  • Modernized logging to use Microsoft.Extensions.Logging

  • Replaced Web API methods with Minimal APIs

✅ Benefits I Saw Firsthand

Using the Upgrade Assistant saved me weeks of effort and helped me maintain confidence throughout the process.

Here’s what I gained:

Benefit Impact
⚙️ Incremental Upgrades Focused on one project at a time
⏱️ Time Savings Automated 60–70% of migration work
🧠 Developer Awareness Better understanding of what changed in modern .NET
🔒 Security Moved away from unsupported frameworks
☁️ Cloud-Ready Easy to deploy via Docker + Azure App Service

🧭 My Advice for You

  • Take a backup (or commit everything before you start)

  • Use upgrade-assistant analyze to scan your solution beforehand

  • Upgrade class libraries first, then consumers like web apps

  • Expect manual tweaks—this tool gets you 80% there

  • Don't forget to update your DevOps pipeline, if applicable

🧵 Conclusion

Migrating a large legacy .NET Framework solution to .NET 8 might seem overwhelming—but it doesn't have to be a full rewrite or a leap into the unknown. With the .NET Upgrade Assistant, I found a structured, guided path that made the journey manageable and insightful.

It won’t magically fix every line of code, but it will illuminate the path, project by project, and help you bring your software into the modern .NET era.

If you're holding off on your upgrade—this is your sign to get started.

🧰 Helpful Links


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