need impact analysis

Hello @Sridhar S ,

Thanks for your question.

Upgrading all your EOL .NET Core apps to the latest LTS is generally the right move, but it can have some negative impacts.

• Some APIs have been removed or changed, and newer patterns (such as the minimal hosting model in ASP.NET Core) are now preferred. Existing code (For ex: Startup.cs) may still work but might need refactoring depending on your target version.
• Older NuGet packages may not support newer .NET versions, which could require upgrading or replacing those libraries.
• You may need to update your hosting environment (OS, Docker images, CI/CD pipelines,...), as newer .NET versions drop support for older platforms.

I recommend that you don't jump straight from an EOL version to .NET 10 in one go. Go incrementally and test at each step.

I hope this addresses your question. If this response was helpful, please consider following the guidance to provide feedback.

Upgrading .NET Core apps that are on (or approaching) end of support to the latest LTS (.NET 10) is generally positive and recommended, but there are impacts to plan for.

Key positive impacts:

1. Support and security
   .NET 10 is an LTS release supported for three years, so upgrading removes EOL risk and ensures security fixes and servicing updates continue to be available.
2. Performance and runtime improvements
   .NET 10 includes runtime optimizations (JIT inlining, devirtualization, stack allocations, AVX10.2, NativeAOT enhancements, better loop optimization) and library improvements (cryptography, networking, JSON, process management). These can improve throughput, latency, and resource usage compared to older .NET Core versions.
3. New APIs and features
   New APIs in cryptography, globalization, numerics, serialization, collections, diagnostics, networking, and JSON give more capabilities without additional dependencies.
4. Easier long‑term maintenance
   Moving to the latest LTS reduces the frequency of major upgrades and aligns with the current support policy.

Key risks / negative impacts to plan for:

1. Breaking changes
   Each major .NET version can introduce breaking changes. When jumping from older .NET Core versions to .NET 10, multiple version steps are crossed, so more breaking changes may apply. The official guidance is to review the “Breaking changes in .NET” documentation for each version between the current runtime and .NET 10 and test thoroughly.
2. Package and framework compatibility
   Starting with .NET 6, core library packages no longer support target frameworks older than .NET Framework 4.6.1, .NET Core 3.1, or .NET Standard 2.0. If any projects still target older TFMs or rely on packages that have not been updated for modern .NET, those packages may no longer update or may not be compatible. In evolving projects, upgrading the target framework is recommended so that packages can be serviced.
3. EF Core and other library version alignment
   EF Core and other major libraries track recent .NET versions. For example, EF Core 8 and 9 target .NET 8. When moving to .NET 10, EF Core and other dependencies may also need to be upgraded to supported versions that align with the new runtime. This can introduce additional breaking changes at the library level.
4. Tooling and environment updates
   Development and build environments must be updated to the .NET 10 SDK. CI/CD agents, container images, and local developer machines need the new SDK/runtime. Visual Studio or other IDEs may need to be updated to versions that support .NET 10.
5. Testing and validation effort
   The main “cost” is the engineering effort: assessing the current apps, updating project files/TFMs, resolving API and package issues, and performing regression testing. This is not a runtime penalty but an upgrade project cost.

Mitigation and approach:

1. Use the official upgrade guidance to:
   • Assess current apps and dependencies.
   • Choose an upgrade path (direct to .NET 10 or staged via intermediate versions if needed).
   • Modernize where appropriate (containers, cloud patterns) while upgrading.
2. Keep developer tools and SDKs up to date so that new language and runtime features are available and security issues are addressed.
3. For libraries owned internally, consider the impact of breaking changes on downstream projects and use techniques like parallel APIs or multi‑targeting where appropriate.

In summary, there is no inherent runtime “negative impact” expected from moving EOL .NET Core apps to .NET 10 LTS; the main risks are compatibility and breaking changes, which can be managed with proper planning, dependency review, and testing.

References:

• Overview of upgrading .NET apps
• Upgrade to a new .NET version
• What's new in .NET 10
• .NET implementations supported by EF Core
• Older framework versions dropped from package
• Version and update considerations for C# developers
• What's new in ASP.NET Core in .NET 10