ASP.NET Core 3.0 only runs on .NET Core

## ASP.NET Core 3.0 only runs on .NET Core

_This change is one of several which were [announced on the ASP.NET blog.][aspnet-blog]_

The .NET Framework will get fewer of the newer platform and language features that come to .NET Core moving forward, due to the in-place update nature of .NET Framework and the desire to limit changes there that might break existing applications. To ensure ASP.NET Core can fully leverage the improvements coming to .NET Core moving forward, ASP.NET Core will only run on .NET Core starting from 3.0. Moving forward, you can simply think of ASP.NET Core as being part of .NET Core.

Customers utilizing ASP.NET Core on .NET Framework today can continue to do so in a fully supported fashion using the [2.1 LTS release][2.1-lts]. Support and servicing for 2.1 will continue until at least August 21, 2021 (3 years after its declaration as an LTS release) in accordance with the [.NET Support Policy](https://www.microsoft.com/net/platform/support-policy). In addition, support for ASP.NET Core 2.1 packages **on .NET Framework** will extend indefinitely, similar to the [servicing policy for other package-based ASP.NET frameworks](https://dotnet.microsoft.com/platform/support/policy/aspnet).

For more information about porting from .NET Framework to .NET Core, see our documentation on [Porting to .NET Core.](https://docs.microsoft.com/en-us/dotnet/core/porting/).

**Please note** that this does not affect the following:
 
 * **Microsoft.Extensions** packages (such as logging, dependency injection, and config) will continue to support .NET Standard
 * **Entity Framework Core** will continue to support .NET Standard

Please see [the original blog post][aspnet-blog] for more details on the motivation for this change.

[2.1-lts]: https://www.microsoft.com/net/download/dotnet-core/2.1
[dotnet-blog]: https://blogs.msdn.microsoft.com/dotnet/2018/10/04/update-on-net-core-3-0-and-net-framework-4-8/
[aspnet-blog]: https://blogs.msdn.microsoft.com/webdev/2018/10/29/a-first-look-at-changes-coming-in-asp-net-core-3-0
[discussion]: https://github.com/aspnet/AspNetCore/issues/3753

### Version introduced

3.0

### Old behavior

ASP.NET Core applications could run on either .NET Core or .NET Framework.

### New behavior

ASP.NET Core applications can only be run on .NET Core.

### Reason for change

.NET Framework will get fewer of the newer platform and language features that come to .NET Core moving forward, due to the in-place update nature of .NET Framework and the desire to limit changes there that might break existing applications. To ensure ASP.NET Core can fully leverage the improvements coming to .NET Core moving forward, ASP.NET Core will only run on .NET Core.

### Recommended action

- Keep your application on ASP.NET Core 2.1
- Migrate your application and dependencies to .NET Core

### Category

- ASP.NET Core

### Affected APIs

Not detectable via API analysis



---
#### Issue metadata

* Issue type: breaking-change

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ASP.NET Core 3.0 only runs on .NET Core #14717