Introduction
As part of the key team overseeing .NET projects at Bacancy, I have handled many .NET migrations over the years, both small and large. Some were just simple version upgrades, and some involved modernizing old monolithic applications that carried years of legacy dependencies.
Over time, I have accumulated enough experience which helps me understand what works and what won’t in these migration projects.
Through these projects, I’ve learned what actually works in practice and what tends to cause trouble, so I’m sharing some of the key .NET migration best practices here. These practices have helped me reduce risk, manage the workload, and move applications to a modern .NET stack smoothly.
Top 10 .NET Migration Best Practices to Follow
I have explained each of the ten best practices for .NET migration in detail, and I have also shared insights from my experience as a part of the team handling these projects at my firm, so you can get a clear idea of what works and what doesn't.
1. Assess the Existing Codebase Thoroughly
Before even touching a single line of code, I spend time understanding the current application. I map out dependencies, check which libraries are outdated, and identify areas that are delicate to mess with or tightly coupled.
In one migration project, we discovered a legacy logging library that wasn’t compatible with the target .NET version. By spotting it early, we avoided weeks of troubleshooting and rewrote only the affected parts. This assessment stage also helps prioritize what can be migrated as it is, what needs a rewrite, and what requires extra testing.
2. Define Clear Goals for the Migration
As an organization spending money and resources on the process, you need to be clear why you are making the move. Are you upgrading to .NET 8 for performance improvements? Are you modernizing architecture for easier maintenance? Having a clear “WHY” behind your action is actually one of the key best practices for .NET migration that helps avoid deviating from the scope of the projects and make consistent decisions throughout the migration.
I always document what success looks like. For example, in a project for a financial client, our goal was to cut build times in half and improve service reliability. With these targets in mind, we made choices about which modules to refactor and which libraries to replace, keeping the migration focused and measurable.
3. Keep Dependencies in Check
Third-party libraries and NuGet packages can make or break a migration. I audit every dependency, check its compatibility with the target .NET version, and remove anything unnecessary.
On one project, an old XML parsing library caused subtle runtime errors after migration. By identifying it early and switching to a supported alternative, we avoided production incidents and reduced unexpected debugging later. Dependencies often hide surprises, so keeping them under control is critical.
4. Modularize Where Possible
Even if the application is a monolith, I try to organize the code into modules or logical layers. You don’t have to move to full microservices, but isolating components makes migration safer.
When clients come to us for .NET migration services, we often recommend modularizing their applications as part of the project scope. For instance, in a healthcare system migration, I remember our strategy to separate the billing module from patient records. This strategy actually allowed us to migrate and test billing functionality independently, ensuring that critical patient data services remained unaffected.
Modularization reduces risk, improves clarity for the client, and enables multiple teams to work in parallel without stepping on each other’s work.
5. Prioritize Automated Testing
Migration without a solid test suite is risky. I focus on ensuring unit and integration tests cover critical paths before upgrading.
In one retail project, the team had almost no automated tests. We added tests around core inventory and checkout functionality. When we moved to .NET 8, these tests caught subtle changes in behavior caused by library updates, saving us from releasing broken features to production.
6. Handle Configuration Separately
Hardcoded settings, connection strings, and environment-specific configurations are common sources of errors. As a critical .NET migration best practice, I make it a rule to externalize configurations before migration.
For example, during a migration of a logistics platform, we moved all environment-specific settings to configuration files and environment variables. This allowed us to deploy the same code to staging, testing, and production without touching the source code, which eliminated a lot of last-minute surprises.
7. Monitor Performance Early
I always benchmark critical components on the current .NET version. After migration, I compare metrics immediately to detect regressions or improvements.
In a financial trading platform, we noticed a particular calculation module slowed down slightly after upgrading libraries. Because we had baseline metrics, we pinpointed the cause and optimized the code. Without early monitoring, this slowdown might have gone unnoticed until customers complained.
8. Update CI/CD Pipelines
Your pipelines should reflect the new environment. Sometimes, updating the SDK in your build image is enough; other times, scripts for deployment or testing need rewriting.
During one enterprise migration to .NET 10, the CI/CD pipelines were outdated and relied on deprecated PowerShell scripts. Updating the pipelines alongside the migration prevented failed builds and ensured developers could deploy confidently.
9. Communicate with the Team
Migration affects multiple teams. Developers, QA, and operations all need to know what is changing and when. Clear communication prevents duplicated work and helps everyone validate their areas correctly.
I usually hold short syncs every few days and maintain a shared document detailing migration progress, issues, and responsibilities. In a large-scale insurance application migration, this communication approach prevented confusion across five different teams working in parallel.
10. Plan for Rollback and Recovery
Even with thorough preparation, things can fail. So, having a rollback plan ready is an important .NET migration best practice that I follow and will recommend to you all too. This rollback and recovery plan might involve backups, database snapshots, or feature toggles that allow the previous version to be restored quickly.
In one migration, a critical module failed in production due to a minor configuration mismatch. Because we had a rollback plan, the previous version was restored in under an hour, avoiding significant disruption. Planning for recovery gives the team confidence to proceed without the fear of any loss.
Final Thoughts
A .NET migration works best when you follow clear steps, keep the application stable, and handle tricky areas like dependencies, testing, and configurations carefully. These are the .NET migration best practices that work for me as well as the team across projects, and make the process predictable instead of chaotic.
Having shared these best practices, Here’s an insider tip that I would like to share with you all.
Instead of trying to do this all on your own, you should hire .NET developers who have proven experience handling migration projects, as they know where issues usually crop up, how to structure code safely, and how to keep systems running while migrating. Taking expert help can make sure that your project stays on track and delivers desired results.
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