.NET Core 3 will not run on .NET Framework

Until now, it was possible to run .NET Core code on .NET Framework. All you needed to do is go to your project file and change the project type from "netcoreapp" to one of the .NET Framework version identifiers, such as "net471".

If you do this, you will then have a much nicer "SDK" project structure, wouldn't have to unload your project file to make edits to it and have a much cleaner code, especially if you are working on a web-hosted ASP.NET application.

However, with the upcoming release of .NET Core 3, this will change. You will no longer be allowed to run .NET Core code on .NET Framework.

This change is being introduced to decouple .NET Core from .NET Framework. As Microsoft has announced, the company is planning to let its older programming platform die a gradual death.

Of course, .NET Framework will still be updated from time to time. But those updates will not do anything more than fixing bugs and bringing certain features of the platform, such as its security standards, up to date. .NET Core, on the other hand, will have completely new features developed for it, as it is intended to eventually become the main programming platform in Microsoft stack.

The good news is that there isn't anything planned to be added to .NET Core 3 that .NET Framework doesn't have already. And, with the current version of .NET Core, 2.1, being officially supported until the 21st of August 2021, developers can still take advantage of .NET Core features in their .NET Framework apps. However, Microsoft strongly recommends that .NET Core should be used for any new projects, unless the project specifically requires features that only .NET Framework has.