This article is part of a series on Migrating from .NET Framework to .NET, also available as a chapter in our free, downloadable eBook

When does .NET Core 3.1 lose support? Is .NET Framework 4.7’s support tied to its operating system? Is .NET 5 needed to upgrade to .NET 10?

The questions surrounding .NET support are as diverse as their users. No one article could cover all the possibilities.

That said, we’ve identified four common questions .NET developers are asking online when asking about long-term support. Large enterprises that’ve had trouble migrating their libraries to newer frameworks are still working on older .NETs. This article is focused on those who haven’t upgraded to .NET 10 yet.

Here are our concise answers.

What .NET should I use for my new applications?

The answer isn’t automatically “the latest and greatest”. Ultimately this will depend on several factors, and maintaining consistency and using technology that developers are comfortable with is often more important than using the latest version.

Say you upgraded to .NET 5 in 2020 and were very satisfied. Now that .NET 10 is out, you’re thinking about using it for your new application exclusively. There’s no issue with this, but since you’ve already upgraded your libraries to .NET 5 it’s a cakewalk to move everything to .NET 10 (especially if you followed our advice for migrating libraries).

After you’ve made the transition to the current .NET (.NET 5 to .NET 10) , upgrading to the new iterations is easy.

• If you’re still working in .NET Framework 3.5 or 4.8, you’re covered until the operating system loses support. So a new application could use Framework 3.5, and it might make sense if that application will be substantially similar to another application on Framework 3.5.
• If you’re working with .NET versions like .NET Core 3.0, you should definitely consider migrating to .NET 6 for your new applications; it’s much closer technologically speaking than .NET Framework 3.5 to 4.8. You also may be working with a version of .NET that’s out-of-support.

Check out our article about .NET support and end-of-life dates for more details.

When should I upgrade my .NET’s minor version?

.NET is a funny little framework when it comes to naming. Some “major version number” differences (like .NET Framework 2.0 to 3.5) have minor changes, while some “patch version number” differences (like 4.5.1 to 4.5.2) have major, breaking changes.

So, when should you upgrade your minor version? It depends on the version you’re using now:

• .NET Framework 3.0: upgrade to 3.5 ASAP
• .NET Framework 4.0 to 4.6.1: upgrade to 4.8 ASAP
• .NET Framework 4.6.2 to 4.7: upgrade to 4.8 as time permits
• .NET Core 3.0: upgrade to .NET ASAP

These four are the latest minor versions and are guaranteed long-term support thanks to their tie to operating system support. Out-of-support versions will still work, but you will miss important security and bug fixes.

No out-of support versions since .NET 5 have had a minor update release, as of publication.

When should I upgrade my .NET’s patch version?

If you’re not operating on .NET, the sooner the better.

We’ve seen the ‘Patch Tuesdays lead to bad Wednesdays’ memes before, so don’t rush into patch upgrades if you don’t have time to deal with possible breaks.

On the bright side, there’s no rush with .NET when it comes to patches.

Consider doing more research to see if these patches are worth the resources.

Can I still use different .NET platforms for different applications?

Until the older .NETs (Framework 4.8, etc.) reach their end of life they can be used.

Core and Framework were developed in parallel, so if you were using both during the height of their support to develop different applications, continuing to do so isn’t an issue.

That said, the clear future is the new .NET. The release of .NET 5 signaled that there is no more parallel development track for .NET development. Once you make the migration to .NET, it’s better to use one platform for all applications.

LTS Takeaways

We won’t leave you hanging. To answer our opening questions:

• When did .NET Core 3.1 lose support? December 3, 2022. Start considering migration plans now!
• Is .NET Framework 4.7’s support tied to its operating system? Yes! It follows the lifecycle policy of its parent OS.
• Is .NET 5 needed to upgrade to .NET 10? No, you can skip .NET 5 and go straight to .NET 10!

There is a lot to talk about when it comes to .NET long-term support, like maintaining applications running on deprecated frameworks, or using CI/CD practices to help keep up with the new annual release cadence.

Wow, we really covered a lot today! It’s worth bookmarking this page to keep these common migration questions and answers nearby! Better yet, check out our .NET Migration Guide, which dives deeper into LTS, understanding SemVer for NuGet, implementing microservices, estimating migration timelines, and more. Download your free copy today!