.NET 10 Is Here: A Practical Upgrade Walkthrough

Introduction

A new .NET release is an opportunity to improve application performance, maintainability, and long-term supportability. However, upgrading an existing application requires more than installing a new SDK and changing its target framework.

A reliable upgrade process combines dependency checks, code analysis, automated tests, deployment validation, and a rollback plan. This walkthrough outlines a practical approach for moving an existing application to .NET 10.

1. Confirm the starting point

Before changing the project, identify the current target framework, installed SDK, hosting environment, and major dependencies.

Check the installed SDKs:

dotnet --list-sdks

Inspect the project’s target framework and any SDK version restrictions in global.json. If the project uses multiple libraries, applications, and test projects, inventory all of them rather than upgrading only the main web application.

Also capture a baseline of build results, test failures, memory usage, and response times for critical endpoints.

2. Update the target framework

A project targeting .NET 8 might contain:

<PropertyGroup>
  <TargetFramework>net8.0</TargetFramework>
</PropertyGroup>

When the application is ready, change it to:

<PropertyGroup>
  <TargetFramework>net10.0</TargetFramework>
</PropertyGroup>

Install the appropriate .NET 10 SDK and ensure that CI and deployment environments can build and run the application.

For ASP.NET Core applications, review the hosting model, middleware pipeline, configuration, authentication, and any APIs affected by framework changes. Follow the official migration guidance for the exact source and target versions.

3. Review dependencies before upgrading everything

Use the package tooling to inspect outdated and vulnerable dependencies:

dotnet list package --outdated
dotnet list package --vulnerable --include-transitive

Check whether important packages support the target framework. Prioritize packages involved in database access, authentication, serialization, logging, and HTTP communication.

Upgrade related packages in manageable groups. If the application breaks, smaller changes make it easier to identify which dependency or API change caused the problem.

4. Build and test incrementally

After updating the target framework and dependencies, restore and build:

dotnet restore
dotnet build --no-restore
dotnet test

Run these commands from the appropriate solution or project directory. A successful build proves that the code compiles, but it does not prove that the application behaves correctly.

Pay particular attention to:

• Authentication and authorization policies.
• JSON serialization and API contracts.
• Database migrations and transaction behavior.
• Background workers and application shutdown.
• Configuration and secrets loading.
• HTTP timeouts and error handling.

Add integration tests for critical paths that depend on framework behavior or external infrastructure.

5. Measure performance rather than assuming improvements

A newer runtime may improve some workloads, but the results depend on the application. Compare the upgraded version with the baseline using representative traffic and equivalent infrastructure.

Measure request latency, throughput, memory consumption, startup time, and error rates. Avoid relying on a single synthetic benchmark to make broad claims about production performance.

If a regression appears, profile the application and investigate it before deploying widely.

6. Deploy safely

Use a staging environment that resembles production. Verify health checks, logging, metrics, certificates, configuration, and database compatibility.

For production, use a rollout strategy appropriate to the system, such as a canary deployment or a gradual replacement of instances. Define rollback criteria in advance and be careful with database migrations that are not backward-compatible with the previous application version.

Conclusion

.NET 10 adoption should be treated as a controlled engineering change. Upgrade the framework and dependencies deliberately, test real application behavior, measure performance, and validate deployment before expanding the rollout.